[Appendix A] What's on the Companion Disk? [Appendix A] What's on the Companion Disk? Table of Contents A. What's on the Companion Disk?..................................................................................................................2 A.1 Installing the Guide...........................................................................................................................2 ...............................................................................................................................................................................3 A.2 Using the Guide................................................................................................................................3 ...............................................................................................................................................................................5 B. Calling Stored Procedures from PL/SQL Version 1.1................................................................................6 B.1 Using Stubs to Talk to Server−Side PL/SQL ....................................................................................7 ...............................................................................................................................................................................9 B.2 Restrictions on Calling Stored Procedures........................................................................................9 B.2.1 No Server−Side PL/SQL Datatypes..................................................................................9 B.2.2 No Direct Stored Package Variable References ..............................................................10 B.2.3 No Direct Remote Procedure Calls.................................................................................12 B.2.4 No Default Parameter Values ..........................................................................................12 .............................................................................................................................................................................14 C. Built−In Packages........................................................................................................................................15 C.1 Using the Built−in Packages...........................................................................................................16 .............................................................................................................................................................................18 C.2 DBMS_ALERT ...............................................................................................................................18 C.2.1 The REGISTER procedure.............................................................................................18 C.2.2 The REMOVE procedure ................................................................................................18 C.2.3 The REMOVEALL procedure........................................................................................18 C.2.4 The SET_DEFAULTS procedure...................................................................................18 C.2.5 The SIGNAL procedure..................................................................................................18 C.2.6 The WAITANY procedure.............................................................................................19 C.2.7 The WAITONE procedure..............................................................................................19 .............................................................................................................................................................................20 C.3 Oracle AQ, the Advanced Queueing Facility ..................................................................................20 C.3.1 DBMS_AQ (PL/SQL 8 Only) .........................................................................................20 C.3.2 DBMS_AQADM (PL/SQL 8 Only)...............................................................................21 .............................................................................................................................................................................24 C.4 DBMS_DDL...................................................................................................................................24 C.4.1 The ALTER_COMPILE procedure................................................................................24 C.4.2 The ANALYZE_OBJECT procedure.............................................................................24 .............................................................................................................................................................................25 C.5 DBMS_ JOB...................................................................................................................................25 C.5.1 The BROKEN procedure................................................................................................25 C.5.2 The CHANGE procedure................................................................................................25 C.5.3 The INTERVAL procedure .............................................................................................25 C.5.4 The ISUBMIT procedure................................................................................................25 C.5.5 The NEXT_DATE procedure.........................................................................................26 C.5.6 The REMOVE procedure ................................................................................................26 C.5.7 The RUN procedure........................................................................................................26 C.5.8 The SUBMIT procedure.................................................................................................26 C.5.9 The USER_EXPORT procedure.....................................................................................26 C.5.10 The WHAT procedure ...................................................................................................26 .............................................................................................................................................................................28 C.6 DBMS_LOB (PL/SQL8 Only).......................................................................................................28 C.6.1 The APPEND procedure.................................................................................................28 C.6.2 The COMPARE function................................................................................................28 C.6.3 The COPY procedure......................................................................................................29 i [Appendix A] What's on the Companion Disk? Table of Contents C.6.4 The ERASE procedure....................................................................................................29 C.6.5 The FILECLOSE procedure...........................................................................................29 C.6.6 The FILECLOSEALL procedure ....................................................................................29 C.6.7 The FILEEXISTS function.............................................................................................29 C.6.8 The FILEGETNAME procedure .....................................................................................29 C.6.9 The FILEISOPEN function.............................................................................................30 C.6.10 The FILEOPEN procedure ............................................................................................30 C.6.11 The GETLENGTH function.........................................................................................30 C.6.12 The INSTR function ......................................................................................................30 C.6.13 The READ procedure ....................................................................................................30 C.6.14 The SUBSTR function..................................................................................................31 C.6.15 The TRIM procedure .....................................................................................................31 C.6.16 The WRITE procedure..................................................................................................31 .............................................................................................................................................................................33 C.7 DBMS_LOCK .................................................................................................................................33 C.7.1 The ALLOCATE_UNIQUE procedure..........................................................................33 C.7.2 The CONVERT function................................................................................................33 C.7.3 The RELEASE function ..................................................................................................34 C.7.4 The REQUEST function.................................................................................................34 C.7.5 The SLEEP procedure.....................................................................................................34 .............................................................................................................................................................................36 C.8 DBMS_MAIL.................................................................................................................................36 C.8.1 The SEND procedure......................................................................................................36 .............................................................................................................................................................................37 C.9 DBMS_OUTPUT............................................................................................................................37 C.9.1 The DISABLE procedure ................................................................................................37 C.9.2 The ENABLE procedure.................................................................................................37 C.9.3 The GET_LINE procedure ..............................................................................................37 C.9.4 The GET_LINES procedure...........................................................................................37 C.9.5 The NEW_LINE procedure............................................................................................37 C.9.6 The PUT procedure.........................................................................................................38 C.9.7 The PUT_LINE procedure..............................................................................................38 .............................................................................................................................................................................39 C.10 DBMS_PIPE.................................................................................................................................39 C.10.1 The CREATE_PIPE function.......................................................................................39 C.10.2 The NEXT_ITEM_TYPE function...............................................................................39 C.10.3 The PACK_MESSAGE procedure...............................................................................40 C.10.4 The PURGE procedure.................................................................................................40 C.10.5 The RECEIVE_MESSAGE function ............................................................................40 C.10.6 The REMOVE_PIPE function......................................................................................40 C.10.7 The RESET_BUFFER procedure.................................................................................40 C.10.8 The SEND_MESSAGE function..................................................................................41 C.10.9 The UNIQUE_SESSION_NAME function..................................................................41 C.10.10 The UNPACK_MESSAGE procedure.......................................................................41 .............................................................................................................................................................................42 C.11 DBMS_ROWID (PL/SQL8 Only)................................................................................................42 C.11.1 The ROWID_CREATE function..................................................................................42 C.11.2 The ROWID_INFO procedure ......................................................................................42 C.11.3 The ROWID_TYPE function ........................................................................................42 C.11.4 The ROWID_OBJECT function...................................................................................42 C.11.5 The ROWID_RELATIVE_FNO function....................................................................43 C.11.6 The ROWID_BLOCK_NUMBER function.................................................................43 ii [Appendix A] What's on the Companion Disk? Table of Contents C.11.7 The ROWID_ROW_NUMBER function.....................................................................43 C.11.8 The ROWID_TO_ABSOLUTE_FNO function...........................................................43 C.11.9 The ROWID_TO_EXTENDED function.....................................................................43 C.11.10 The ROWID_TO_RESTRICTED function................................................................43 C.11.11 The ROWID_VERIFY function.................................................................................43 .............................................................................................................................................................................45 C.12 DBMS_SESSION.........................................................................................................................45 C.12.1 The CLOSE_DATABASE_LINK procedure...............................................................45 C.12.2 The IS_ROLE_ENABLED function .............................................................................45 C.12.3 The RESET_PACKAGE procedure.............................................................................45 C.12.4 The SET_LABEL procedure .........................................................................................45 C.12.5 The SET_NLS_LABEL procedure...............................................................................45 C.12.6 The SET_NLS procedure..............................................................................................45 C.12.7 The SET_ROLE procedure...........................................................................................46 C.12.8 The SET_SQL_TRACE procedure...............................................................................46 C.12.9 The UNIQUE_SESSION_ID function.........................................................................46 .............................................................................................................................................................................47 C.13 DBMS_SNAPSHOT.....................................................................................................................47 C.13.1 The DROP_SNAPSHOT procedure.............................................................................47 C.13.2 The GET_LOG_AGE procedure..................................................................................47 C.13.3 The PURGE_LOG procedure.......................................................................................47 C.13.4 The REFRESH procedure.............................................................................................47 C.13.5 The REFRESH_ALL procedure...................................................................................48 C.13.6 The SET_UP procedure................................................................................................48 C.13.7 The WRAP_UP procedure............................................................................................48 .............................................................................................................................................................................49 C.14 DBMS_SQL..................................................................................................................................49 C.14.1 The BIND_ARRAY procedure.....................................................................................49 C.14.2 The BIND_VARIABLE procedure ...............................................................................49 C.14.3 The CLOSE_CURSOR procedure................................................................................50 C.14.4 The COLUMN_VALUE procedure ..............................................................................50 C.14.5 The DEFINE_COLUMN procedure.............................................................................51 C.14.6 The EXECUTE function...............................................................................................51 C.14.7 The EXECUTE_AND_FETCH function ......................................................................52 C.14.8 The FETCH_ROWS function.......................................................................................52 C.14.9 The IS_OPEN function.................................................................................................52 C.14.10 The LAST_ERROR_POSITION function ..................................................................52 C.14.11 The LAST_ROW_COUNT function..........................................................................52 C.14.12 The LAST_ROW_ID function ....................................................................................52 C.14.13 The LAST_SQL_FUNCTION_CODE function .........................................................52 C.14.14 The OPEN_CURSOR function...................................................................................53 C.14.15 The PARSE procedure................................................................................................53 C.14.16 The VARIABLE_VALUE procedure.........................................................................53 .............................................................................................................................................................................54 C.15 DBMS_TRANSACTION.............................................................................................................54 C.15.1 The ADVISE_COMMIT procedure.............................................................................54 C.15.2 The ADVISE_NOTHING procedure ............................................................................54 C.15.3 The ADVISE_ROLLBACK procedure........................................................................54 C.15.4 The COMMIT procedure..............................................................................................55 C.15.5 The COMMIT_COMMENT procedure ........................................................................55 C.15.6 The COMMIT_FORCE procedure...............................................................................55 C.15.7 The READ_ONLY procedure .......................................................................................55 iii [Appendix A] What's on the Companion Disk? Table of Contents C.15.8 The READ_WRITE procedure.....................................................................................55 C.15.9 The ROLLBACK procedure.........................................................................................56 C.15.10 The ROLLBACK_FORCE procedure........................................................................56 C.15.11 The ROLLBACK_SAVEPOINT procedure...............................................................56 C.15.12 The SAVEPOINT procedure......................................................................................56 C.15.13 The USE_ROLLBACK_SEGMENT procedure .........................................................56 C.15.14 The BEGIN_DISCRETE_TRANSACTION procedure.............................................56 C.15.15 The PURGE_MIXED procedure................................................................................57 C.15.16 The PURGE_LOST_DB procedure............................................................................57 C.15.17 The LOCAL_TRANSACTION_ID function.............................................................57 C.15.18 The STEP_ID function ................................................................................................57 .............................................................................................................................................................................59 C.16 DBMS_UTILITY..........................................................................................................................59 C.16.1 The ANALYZE_SCHEMA procedure.........................................................................59 C.16.2 The COMMA_TO_TABLE procedure.........................................................................59 C.16.3 The COMPILE_SCHEMA procedure..........................................................................59 C.16.4 The FORMAT_CALL_STACK function.....................................................................59 C.16.5 The FORMAT_ERROR_STACK function..................................................................59 C.16.6 The GET_TIME function ..............................................................................................60 C.16.7 The IS_PARALLEL_SERVER function......................................................................60 C.16.8 The NAME_RESOLVE procedure...............................................................................60 C.16.9 The NAME_TOKENIZE procedure.............................................................................60 C.16.10 The PORT_STRING function .....................................................................................61 C.16.11 The TABLE_TO_COMMA procedure.......................................................................61 .............................................................................................................................................................................62 C.17 UTL_FILE .....................................................................................................................................62 C.17.1 Setting Up UTL_FILE..................................................................................................62 .............................................................................................................................................................................65 1. Introduction to PL/SQL...............................................................................................................................66 1.1 What Is PL/SQL?.............................................................................................................................66 .............................................................................................................................................................................68 1.2 The Concept of Programming in Oracle Applications....................................................................68 .............................................................................................................................................................................70 1.3 The Origins of PL/SQL ....................................................................................................................70 1.3.1 Improved Application Portability with PL/SQL ..............................................................70 1.3.2 Improved Execution Authority and Transaction Integrity with PL/SQL........................71 .............................................................................................................................................................................72 1.4 PL/SQL Versions.............................................................................................................................72 1.4.1 Working with Multiple Versions of PL/SQL..................................................................72 1.4.2 How This Book Handles Different Versions of PL/SQL................................................73 1.4.3 PL/SQL Version 2.0........................................................................................................73 1.4.4 PL/SQL Release 2.1 .........................................................................................................80 1.4.5 PL/SQL Release 2.2 .........................................................................................................82 1.4.6 PL/SQL Release 2.3 .........................................................................................................83 1.4.7 PL/SQL Version 8.0........................................................................................................84 1.4.8 PL/SQL Release 1.1 .........................................................................................................86 .............................................................................................................................................................................88 1.5 Advice for Oracle Programmers......................................................................................................88 1.5.1 Take a Creative, Even Radical Approach........................................................................88 1.5.2 Get Ready to Establish New Habits .................................................................................88 1.5.3 Assume that PL/SQL Has What You Need.....................................................................89 iv [Appendix A] What's on the Companion Disk? Table of Contents 1.5.4 Share Your Ideas ..............................................................................................................90 .............................................................................................................................................................................91 1.6 A Few of My Favorite (PL/SQL) Things........................................................................................91 1.6.1 Anchored declarations.....................................................................................................91 1.6.2 Built−in functions............................................................................................................91 1.6.3 Built−in packages............................................................................................................91 1.6.4 The cursor FOR loop.......................................................................................................92 1.6.5 Scoping with nested blocks ..............................................................................................92 1.6.6 Module overloading.........................................................................................................92 1.6.7 Local modules..................................................................................................................93 1.6.8 Packages ...........................................................................................................................93 .............................................................................................................................................................................95 1.7 Best Practices for PL/SQL Excellence............................................................................................95 1.7.1 Write as Little Code as Possible......................................................................................95 1.7.2 Synchronize Program and Data Structures......................................................................96 1.7.3 Center All Development Around Packages.....................................................................97 1.7.4 Standardize Your PL/SQL Development Environment..................................................98 . 1.7.5 Structured Code and Other Best Practices.......................................................................98 ...........................................................................................................................................................................101 2. PL/SQL Language Fundamentals.............................................................................................................102 2.1 The PL/SQL Character Set............................................................................................................102 ...........................................................................................................................................................................104 2.2 Identifiers.......................................................................................................................................104 2.2.1 Reserved Words.............................................................................................................105 2.2.2 Whitespace and Keywords .............................................................................................106 ...........................................................................................................................................................................107 2.3 Literals...........................................................................................................................................107 2.3.1 Embedding Single Quotes Inside a String.....................................................................107 2.3.2 Numeric Literals............................................................................................................108 2.3.3 Boolean Literals.............................................................................................................108 ...........................................................................................................................................................................110 2.4 The Semicolon Delimiter...............................................................................................................110 ...........................................................................................................................................................................111 2.5 Comments......................................................................................................................................111 2.5.1 Single−Line Comment Syntax.......................................................................................111 2.5.2 Multiline Comment Syntax ............................................................................................111 ...........................................................................................................................................................................113 2.6 The PRAGMA Keyword...............................................................................................................113 ...........................................................................................................................................................................114 2.7 Block Structure..............................................................................................................................114 2.7.1 Sections of the PL/SQL Block.......................................................................................114 2.7.2 Scope of a Block............................................................................................................115 2.7.3 Nested Blocks................................................................................................................115 ...........................................................................................................................................................................117 3. Effective Coding Style .................................................................................................................................118 3.1 Fundamentals of Effective Layout.................................................................................................118 3.1.1 Revealing Logical Structure with Indentation...............................................................119 3.1.2 Using Case to Aid Readability .......................................................................................120 3.1.3 The UPPER−lower Style...............................................................................................120 3.1.4 Formatting Single Statements........................................................................................121 v [Appendix A] What's on the Companion Disk? Table of Contents 3. Effective Coding Style 3.1.5 Formatting Your Declarations.......................................................................................122 3.1.6 Formatting Multiline Statements...................................................................................123 ...........................................................................................................................................................................126 3.2 Formatting SQL Statements ...........................................................................................................126 ...........................................................................................................................................................................129 3.3 Formatting Control Structures.......................................................................................................129 3.3.1 Formatting IF Statements ...............................................................................................129 3.3.2 Formatting Loops ...........................................................................................................130 3.3.3 Formatting Exception Handlers.....................................................................................131 ...........................................................................................................................................................................133 3.4 Formatting PL/SQL Blocks...........................................................................................................133 ...........................................................................................................................................................................135 3.5 Formatting Packages......................................................................................................................135 ...........................................................................................................................................................................137 3.6 Using Comments Effectively.........................................................................................................137 3.6.1 Comment As You Code.................................................................................................138 3.6.2 Explain the Why −− Not the How −− of Your Program............................................138 3.6.3 Make Comments Easy to Enter and Maintain...............................................................139 3.6.4 Maintain Indentation......................................................................................................140 3.6.5 Comment Declaration Statements.................................................................................141 ...........................................................................................................................................................................143 3.7 Documenting the Entire Package...................................................................................................143 3.7.1 Document the Package Specification............................................................................143 3.7.2 Document the Package Body.........................................................................................144 ...........................................................................................................................................................................146 4. Variables and Program Data.....................................................................................................................147 4.1 Identifiers.......................................................................................................................................147 4.1.1 Choose the Right Name.................................................................................................147 4.1.2 Select Readable Names ..................................................................................................148 ...........................................................................................................................................................................149 4.2 Scalar Datatypes .............................................................................................................................149 4.2.1 Numeric Datatypes........................................................................................................150 4.2.2 Numeric Subtypes..........................................................................................................152 4.2.3 Character Datatypes.......................................................................................................153 4.2.4 The Boolean Datatype...................................................................................................160 4.2.5 The Date−Time Datatype..............................................................................................160 4.2.6 NLS Character Datatypes..............................................................................................161 4.2.7 LOB Datatypes..............................................................................................................162 4.2.8 Conversion Between Datatypes.....................................................................................166 ...........................................................................................................................................................................169 4.3 NULLs in PL/SQL.........................................................................................................................169 4.3.1 NULL Values in Comparisons......................................................................................170 4.3.2 Checking for NULL Values ...........................................................................................170 4.3.3 Function Results with NULL Arguments......................................................................171 ...........................................................................................................................................................................173 4.4 Variable Declarations .....................................................................................................................173 4.4.1 Constrained Declarations...............................................................................................173 4.4.2 Declaration Examples....................................................................................................173 4.4.3 Default Values...............................................................................................................174 4.4.4 NOT NULL Clause ........................................................................................................175 vi [Appendix A] What's on the Companion Disk? Table of Contents 4.5.1 Benefits of Anchored Declarations................................................................................176 4.5.2 Anchoring at Compile Time..........................................................................................176 4.5.3 Nesting Usages of the %TYPE Attribute......................................................................177 4.5.4 Anchoring to Variables in Other PL/SQL Blocks.........................................................178 4.5.5 Anchoring to NOT NULL Datatypes............................................................................179 ...........................................................................................................................................................................179 4.5 Anchored Declarations ...................................................................................................................179 ...........................................................................................................................................................................181 4.6 Programmer−Defined Subtypes .....................................................................................................181 4.6.1 Declaring Subtypes........................................................................................................181 4.6.2 Examples of Subtype Declarations................................................................................182 4.6.3 Emulating Constrained Subtypes...................................................................................183 ...........................................................................................................................................................................185 4.7 Tips for Creating and Using Variables..........................................................................................185 4.7.1 Establish Clear Variable Naming Conventions.............................................................185 4.7.2 Name Subtypes to Self−Document Code......................................................................187 4.7.3 Avoid Recycling Variables............................................................................................188 4.7.4 Use Named Constants to Avoid Hardcoding Values.....................................................188 4.7.5 Convert Variables into Named Constants ......................................................................189 4.7.6 Remove Unused Variables from Programs...................................................................190 4.7.7 Use %TYPE When a Variable Represents a Column ....................................................190 4.7.8 Use %TYPE to Standardize Nondatabase Declarations................................................191 4.7.9 Use Variables to Hide Complex Logic..........................................................................192 ...........................................................................................................................................................................196 5. Conditional and Sequential Control.........................................................................................................197 . 5.1 Conditional Control Statements.....................................................................................................197 5.1.1 The IF−THEN Combination..........................................................................................197 5.1.2 The IF−THEN−ELSE Combination..............................................................................198 5.1.3 The IF−ELSIF Combination..........................................................................................199 5.1.4 Nested IF Statements.....................................................................................................203 ...........................................................................................................................................................................205 5.2 Sequential Control Statements.......................................................................................................205 5.2.1 The GOTO Statement....................................................................................................205 5.2.2 The NULL Statement....................................................................................................208 . ...........................................................................................................................................................................211 6. Database Interaction and Cursors............................................................................................................212 6.1 Transaction Management...............................................................................................................212 6.1.1 The COMMIT Statement...............................................................................................213 6.1.2 The ROLLBACK Statement .........................................................................................213 . 6.1.3 The SAVEPOINT Statement.........................................................................................214 6.1.4 The SET TRANSACTION Statement...........................................................................214 6.1.5 The LOCK TABLE Statement......................................................................................215 ...........................................................................................................................................................................217 6.2 Cursors in PL/SQL .........................................................................................................................217 6.2.1 Types of Cursors............................................................................................................218 6.2.2 Cursor Operations..........................................................................................................218 ...........................................................................................................................................................................220 6.3 Implicit and Explicit Cursors.........................................................................................................220 6.3.1 Implicit Cursors.............................................................................................................220 6.3.2 Drawbacks of Implicit Cursors......................................................................................220 vii [Appendix A] What's on the Companion Disk? Table of Contents 6.3.3 Explicit Cursors.............................................................................................................222 ...........................................................................................................................................................................224 6.4 Declaring Cursors..........................................................................................................................224 6.4.1 The Cursor Name...........................................................................................................224 6.4.2 PL/SQL Variables in a Cursor.......................................................................................225 6.4.3 Identifier Precedence in a Cursor..................................................................................225 . 6.4.4 The Cursor RETURN Clause........................................................................................226 ...........................................................................................................................................................................229 6.5 Opening Cursors............................................................................................................................229 ...........................................................................................................................................................................231 6.6 Fetching from Cursors...................................................................................................................231 6.6.1 Matching Column List with INTO Clause....................................................................231 6.6.2 Fetching Past the Last Row...........................................................................................233 ...........................................................................................................................................................................234 6.7 Column Aliases in Cursors............................................................................................................234 ...........................................................................................................................................................................236 6.8 Closing Cursors ..............................................................................................................................236 6.8.1 Maximum Number of Cursors.......................................................................................236 6.8.2 Closing Local Cursors...................................................................................................237 ...........................................................................................................................................................................238 6.9 Cursor Attributes ............................................................................................................................238 6.9.1 The %FOUND Attribute ................................................................................................239 6.9.2 The %NOTFOUND Attribute.......................................................................................240 6.9.3 The %ROWCOUNT Attribute......................................................................................240 6.9.4 The %ISOPEN Attribute...............................................................................................241 6.9.5 Implicit SQL Cursor Attributes.....................................................................................241 6.9.6 Differences Between Implicit and Explicit Cursor Attributes.......................................241 ...........................................................................................................................................................................243 6.10 Cursor Parameters........................................................................................................................243 6.10.1 Generalizing Cursors with Parameters........................................................................244 6.10.2 Opening Cursors with Parameters...............................................................................244 6.10.3 Scope of Cursor Parameters .........................................................................................245 6.10.4 Cursor Parameter Modes.............................................................................................245 6.10.5 Default Values for Parameters.....................................................................................245 ...........................................................................................................................................................................246 6.11 SELECT FOR UPDATE in Cursors............................................................................................246 6.11.1 Releasing Locks with COMMIT.................................................................................247 6.11.2 The WHERE CURRENT OF Clause..........................................................................248 6.12.1 Features of Cursor Variables.......................................................................................250 6.12.2 Similarities to Static Cursors.......................................................................................250 6.12.3 Declaring REF CURSOR Types and Cursor Variables ...............................................251 6.12.4 Opening Cursor Variables...........................................................................................252 6.12.5 Fetching from Cursor Variables..................................................................................253 6.12.6 Rules for Cursor Variables..........................................................................................254 6.12.7 Passing Cursor Variables as Arguments......................................................................255 6.12.8 Cursor Variable Restrictions ........................................................................................257 ...........................................................................................................................................................................260 6.12 Cursor Variables..........................................................................................................................262 ...........................................................................................................................................................................264 6.13 Working with Cursors..................................................................................................................264 6.13.1 Validating Foreign Key Entry with Cursors................................................................264 6.13.2 Managing a Work Queue with SELECT FOR UPDATE ............................................266 ...........................................................................................................................................................................270 viii [Appendix A] What's on the Companion Disk? Table of Contents 7. Loops............................................................................................................................................................271 7.1 Loop Basics ....................................................................................................................................271 7.1.1 Examples of Different Loops .........................................................................................271 7.1.2 Structure of PL/SQL Loops...........................................................................................272 ...........................................................................................................................................................................274 7.2 The Simple Loop...........................................................................................................................274 7.2.1 Terminating a Simple Loop: EXIT and EXIT WHEN..................................................275 7.2.2 Emulating a REPEAT UNTIL Loop.............................................................................276 ...........................................................................................................................................................................277 7.3 The Numeric FOR Loop................................................................................................................277 7.3.1 Rules for Numeric FOR Loops......................................................................................277 7.3.2 Examples of Numeric FOR Loops .................................................................................278 7.3.3 Handling Nontrivial Increments....................................................................................279 ...........................................................................................................................................................................280 7.4 The Cursor FOR Loop...................................................................................................................280 7.4.1 Example of Cursor FOR Loops.....................................................................................280 7.4.2 The Cursor FOR Loop Record .......................................................................................281 7.4.3 When to Use the Cursor FOR Loop ...............................................................................282 ...........................................................................................................................................................................284 7.5 The WHILE Loop..........................................................................................................................284 7.5.1 The Infinite WHILE Loop.............................................................................................285 ...........................................................................................................................................................................286 7.6 Managing Loop Execution .............................................................................................................286 7.6.1 Loop Labels...................................................................................................................286 7.6.2 Loop Scope....................................................................................................................288 ...........................................................................................................................................................................290 7.7 Tips for PL/SQL Loops.................................................................................................................290 7.7.1 Naming Loop Indexes ....................................................................................................290 7.7.2 The Proper Way to Say Goodbye..................................................................................291 7.7.3 Avoiding the Phony Loop..............................................................................................293 7.7.4 PL/SQL Loops Versus SQL Processing........................................................................293 8.1 Why Exception Handling?.............................................................................................................296 ...........................................................................................................................................................................297 8. Exception Handlers .....................................................................................................................................298 ...........................................................................................................................................................................300 8.2 The Exception Section...................................................................................................................300 ...........................................................................................................................................................................302 8.3 Types of Exceptions .......................................................................................................................302 8.3.1 Named System Exceptions............................................................................................302 8.3.2 Named Programmer−Defined Exceptions.....................................................................304 8.3.3 Unnamed System Exceptions........................................................................................305 8.3.4 Unnamed Programmer−Defined Exceptions.................................................................306 ...........................................................................................................................................................................308 8.4 Determining Exception−Handling Behavior.................................................................................308 8.4.1 Scope of an Exception...................................................................................................308 8.4.2 Propagation of an Exception..........................................................................................312 ...........................................................................................................................................................................315 8.5 Raising an Exception.....................................................................................................................315 8.5.1 Who Raises the Exception?...........................................................................................315 8.5.2 Re−Raising an Exception..............................................................................................316 8.5.3 Exceptions Raised in a Declaration...............................................................................317 ix [Appendix A] What's on the Companion Disk? Table of Contents 8.5.4 Exceptions Raised in an Exception Handler..................................................................317 ...........................................................................................................................................................................320 8.6 Handling Exceptions......................................................................................................................320 8.6.1 Combining Multiple Exceptions in a Single Handler....................................................320 8.6.2 Unhandled Exceptions...................................................................................................321 8.6.3 Using SQLCODE and SQLERRM in WHEN OTHERS Clause..................................321 8.6.4 Continuing Past Exceptions...........................................................................................322 ...........................................................................................................................................................................325 8.7 Client−Server Error Communication.............................................................................................325 8.7.1 Using RAISE_APPLICATION_ERROR......................................................................325 8.7.2 RAISE_APPLICATION_ERROR in a database trigger...............................................325 ...........................................................................................................................................................................327 8.8 NO_DATA_FOUND: Multipurpose Exception............................................................................327 ...........................................................................................................................................................................329 8.9 Exception Handler as IF Statement...............................................................................................329 . ...........................................................................................................................................................................331 8.10 RAISE Nothing but Exceptions...................................................................................................331 ...........................................................................................................................................................................334 9. Records in PL/SQL.....................................................................................................................................335 9.1 Record Basics .................................................................................................................................335 9.1.1 Different Types of Records ............................................................................................335 9.1.2 Accessing Record−Based Data......................................................................................336 9.1.3 Benefits of Using Records.............................................................................................336 9.1.4 Guidelines for Using Records........................................................................................337 9.1.5 Referencing a Record and its Fields..............................................................................338 9.1.6 Comparing Two Records...............................................................................................338 ...........................................................................................................................................................................340 9.2 Table−Based Records....................................................................................................................340 9.2.1 Declaring Records with the %ROWTYPE Attribute....................................................340 ...........................................................................................................................................................................342 9.3 Cursor−Based Records..................................................................................................................342 9.3.1 Choosing Columns for a Cursor Record........................................................................342 9.3.2 Setting the Record's Column Names.............................................................................343 ...........................................................................................................................................................................345 9.4 Programmer−Defined Records......................................................................................................345 9.4.1 Declaring Programmer−Defined Record TYPEs..........................................................345 9.4.2 Declaring the Record.....................................................................................................346 9.4.3 Examples of Programmer−Defined Record Declarations.............................................347 ...........................................................................................................................................................................349 9.5 Assigning Values to and from Records.........................................................................................349 9.5.1 Direct Field Assignment................................................................................................349 9.5.2 SELECT INTO from an Implicit Cursor.......................................................................350 9.5.3 FETCH INTO from an Explicit Cursor.........................................................................350 9.5.4 Aggregate Assignment ..................................................................................................351 . ...........................................................................................................................................................................352 9.6 Record Types and Record Compatibility .......................................................................................352 9.6.1 Assignment Restrictions................................................................................................353 9.6.2 Record Initialization......................................................................................................353 ...........................................................................................................................................................................355 x [Appendix A] What's on the Companion Disk? Table of Contents 9.7 Nested Records..............................................................................................................................355 9.7.1 Example of Nested Records ...........................................................................................355 9.7.2 Dot Notation with Nested Records................................................................................356 9.7.3 Aggregate Assignments of Nested Records ...................................................................356 9.7.4 Denormalizing Program Data with Nested Records......................................................357 10.1 PL/SQL Tables and Other Collections........................................................................................360 10.1.1 PL/SQL Tables............................................................................................................361 10.1.2 Nested Tables and VARRAYs....................................................................................362 ...........................................................................................................................................................................362 10. PL/SQL Tables..........................................................................................................................................362 ...........................................................................................................................................................................363 10.2 Characteristics of PL/SQL Tables...............................................................................................363 ...........................................................................................................................................................................365 10.3 PL/SQL Tables and DML Statements.........................................................................................365 ...........................................................................................................................................................................366 10.4 Declaring a PL/SQL Table ...........................................................................................................366 10.4.1 Defining the Table TYPE............................................................................................366 10.4.2 Declaring the PL/SQL Table.......................................................................................367 ...........................................................................................................................................................................368 10.5 Referencing and Modifying PL/SQL Table Rows .......................................................................368 10.5.1 Automatic Conversion of Row Number Expressions..................................................368 10.5.2 Referencing an Undefined Row ...................................................................................368 10.5.3 Nonsequential Use of PL/SQL Table..........................................................................369 10.5.4 Passing PL/SQL Tables as Parameters........................................................................370 ...........................................................................................................................................................................372 10.6 Filling the Rows of a PL/SQL Table...........................................................................................372 10.6.1 Direct Assignment.......................................................................................................372 10.6.2 Iterative Assignment....................................................................................................372 10.6.3 Aggregate Assignment ................................................................................................373 . ...........................................................................................................................................................................374 10.7 Clearing the PL/SQL Table.........................................................................................................374 ...........................................................................................................................................................................376 10.8 PL/SQL Table Enhancements in PL/SQL Release 2.3................................................................376 10.8.1 PL/SQL Tables of Records..........................................................................................377 10.8.2 PL/SQL Table Built−ins..............................................................................................379 ...........................................................................................................................................................................383 10.9 Working with PL/SQL Tables.....................................................................................................383 10.9.1 Transferring Database Information to PL/SQL Tables ................................................383 10.9.2 Data−Smart Row Numbers in PL/SQL Tables............................................................384 10.9.3 Displaying a PL/SQL Table .........................................................................................386 10.9.4 Building Traditional Arrays with PL/SQL Tables .......................................................391 10.9.5 Optimizing Foreign Key Lookups with PL/SQL Tables.............................................397 ...........................................................................................................................................................................404 11. Character Functions.................................................................................................................................405 11.1 Character Function Descriptions ..................................................................................................406 11.1.1 The ASCII function.....................................................................................................406 11.1.2 The CHR function ........................................................................................................406 11.1.3 The CONCAT function...............................................................................................407 11.1.4 The INITCAP function................................................................................................408 11.1.5 The INSTR function....................................................................................................409 xi [Appendix A] What's on the Companion Disk? Table of Contents 11. Character Functions 11.1.6 The LENGTH function................................................................................................412 11.1.7 The LOWER function ..................................................................................................412 11.1.8 The LPAD function.....................................................................................................413 11.1.9 The LTRIM function...................................................................................................414 11.1.10 The REPLACE function............................................................................................415 11.1.11 The RPAD function...................................................................................................418 11.1.12 The RTRIM function.................................................................................................419 11.1.13 The SOUNDEX function...........................................................................................420 11.1.14 The SUBSTR function...............................................................................................420 11.1.15 The TRANSLATE function .......................................................................................424 11.1.16 The UPPER function.................................................................................................425 ...........................................................................................................................................................................426 11.2 Character Function Examples......................................................................................................426 11.2.1 Parsing a Name............................................................................................................426 11.2.2 Implementing Word Wrap for Long Text...................................................................431 . 11.2.3 Filling Text to Fit a Line..............................................................................................434 11.2.4 Counting Substring Occurrences in Strings.................................................................436 11.2.5 Verifying String Formats with TRANSLATE .............................................................438 ...........................................................................................................................................................................441 12. Date Functions...........................................................................................................................................442 12.1 Date Function Descriptions ..........................................................................................................443 12.1.1 The ADD_MONTHS function....................................................................................443 12.1.2 The LAST_DAY function...........................................................................................444 12.1.3 The MONTHS_BETWEEN function..........................................................................445 12.1.4 The NEW_TIME function...........................................................................................446 12.1.5 The NEXT_DAY function ...........................................................................................447 12.1.6 The ROUND function ..................................................................................................448 12.1.7 The SYSDATE function..............................................................................................450 12.1.8 The TRUNC function..................................................................................................450 ...........................................................................................................................................................................453 12.2 Date Function Examples..............................................................................................................453 12.2.1 Customizing the Behavior of ADD_MONTHS ...........................................................453 12.2.2 Using NEW_TIME in Client−Server Environments...................................................454 ...........................................................................................................................................................................459 13. Numeric, LOB, and Miscellaneous Functions........................................................................................460 13.1 Numeric Function Descriptions...................................................................................................461 13.1.1 The ABS function........................................................................................................461 13.1.2 The ACOS function.....................................................................................................462 13.1.3 The ASIN function .......................................................................................................462 13.1.4 The ATAN function.....................................................................................................462 13.1.5 The ATAN2 function...................................................................................................462 13.1.6 The CEIL function.......................................................................................................463 13.1.7 The COS function........................................................................................................464 13.1.8 The COSH function.....................................................................................................464 13.1.9 The EXP function........................................................................................................464 13.1.10 The FLOOR function.................................................................................................464 13.1.11 The LN function .........................................................................................................465 13.1.12 The LOG function ......................................................................................................465 13.1.13 The MOD function .....................................................................................................465 xii [Appendix A] What's on the Companion Disk? Table of Contents 13. Numeric, LOB, and Miscellaneous Functions 13.1.14 The POWER function................................................................................................465 13.1.15 The ROUND function ................................................................................................466 13.1.16 The SIGN function .....................................................................................................466 13.1.17 The SIN function.......................................................................................................466 13.1.18 The SINH function .....................................................................................................467 13.1.19 The SQRT function ....................................................................................................467 13.1.20 The TAN function ......................................................................................................467 13.1.21 The TANH function...................................................................................................467 13.1.22 The TRUNC function................................................................................................467 13.1.23 Rounding and Truncation with PL/SQL....................................................................468 ...........................................................................................................................................................................469 13.2 LOB Function Descriptions.........................................................................................................469 13.2.1 The BFILENAME function.........................................................................................469 13.2.2 The EMPTY_BLOB function ......................................................................................471 13.2.3 The EMPTY_CLOB function ......................................................................................471 ...........................................................................................................................................................................472 13.3 Miscellaneous Function Descriptions..........................................................................................472 13.3.1 The DUMP function....................................................................................................472 13.3.2 The GREATEST function...........................................................................................473 13.3.3 The LEAST function...................................................................................................473 13.3.4 The NVL function ........................................................................................................473 13.3.5 The SQLCODE function.............................................................................................475 13.3.6 The SQLERRM function.............................................................................................475 13.3.7 The UID function.........................................................................................................476 13.3.8 The USER function ......................................................................................................476 13.3.9 The USERENV function.............................................................................................477 13.3.10 The VSIZE function ...................................................................................................478 ...........................................................................................................................................................................479 14. Conversion Functions...............................................................................................................................480 14.1 Conversion Formats.....................................................................................................................480 14.1.1 Date Format Models....................................................................................................481 14.1.2 Number Format Models...............................................................................................483 ...........................................................................................................................................................................486 14.2 Conversion Function Descriptions ...............................................................................................486 14.2.1 The CHARTOROWID function..................................................................................486 14.2.2 The CONVERT function.............................................................................................486 14.2.3 The HEXTORAW function.........................................................................................486 14.2.4 The RAWTOHEX function.........................................................................................487 14.2.5 The ROWIDTOCHAR function..................................................................................487 14.2.6 The TO_CHAR function (date conversion)................................................................487 . 14.2.7 The TO_CHAR function (number conversion)...........................................................488 14.2.8 The TO_DATE function..............................................................................................488 14.2.9 The TO_NUMBER function.......................................................................................490 ...........................................................................................................................................................................491 14.3 Conversion Function Examples...................................................................................................491 14.3.1 FM: Suppressing Blanks and Zeros.............................................................................491 14.3.2 FX: Matching Formats Exactly ....................................................................................492 14.3.3 RR: Changing Millenia................................................................................................493 14.3.4 Using TO_CHAR to Create a Date Range..................................................................494 14.3.5 Building a Date Manager.............................................................................................498 xiii [Appendix A] What's on the Companion Disk? Table of Contents 15.2.1 Sequence of Section Construction...............................................................................508 15.2.2 PL/SQL Block Structure Examples.............................................................................509 15.3.1 The Structure of an Anonymous Block.......................................................................509 15.3.2 Examples of Anonymous Blocks .................................................................................512 15.3.3 Anonymous Blocks in the Oracle Tools......................................................................512 15.3.4 Nested Blocks..............................................................................................................513 15.3.5 Scope and Visibility.....................................................................................................513 15.3.6 Block Labels................................................................................................................515 15.4.1 Calling a Procedure ......................................................................................................515 15.4.2 Procedure Header .........................................................................................................515 15.4.3 Procedure Body ............................................................................................................516 15.4.4 The END Label............................................................................................................516 ...........................................................................................................................................................................517 15. Procedures and Functions........................................................................................................................521 15.1 Modular Code..............................................................................................................................525 ...........................................................................................................................................................................527 15.2 Review of PL/SQL Block Structure............................................................................................527 ...........................................................................................................................................................................528 15.3 The Anonymous PL/SQL Block..................................................................................................528 ...........................................................................................................................................................................529 15.4 Procedures....................................................................................................................................529 ...........................................................................................................................................................................530 15.5 Functions......................................................................................................................................530 15.5.1 Structure of a Function................................................................................................530 15.5.2 The RETURN Datatype...............................................................................................531 15.5.3 The END Label............................................................................................................532 15.5.4 Calling a Function ........................................................................................................532 15.5.5 Function Header ...........................................................................................................533 15.5.6 Function Body ..............................................................................................................534 15.5.7 A Tiny Function...........................................................................................................534 15.5.8 The RETURN Statement.............................................................................................534 ...........................................................................................................................................................................537 15.6 Parameters....................................................................................................................................537 15.6.1 Defining the Parameters ...............................................................................................537 15.6.2 Parameter Modes.........................................................................................................538 15.6.3 Actual and Formal Parameters .....................................................................................541 15.6.4 Matching Actual and Formal Parameters in PL/SQL..................................................542 15.6.5 Default Values.............................................................................................................544 ...........................................................................................................................................................................545 15.7 Local Modules.............................................................................................................................545 15.7.1 Benefits of Local Modularization................................................................................545 15.7.2 Reducing Code Volume...............................................................................................546 15.7.3 Improving Readability.................................................................................................546 15.7.4 Bottom−Up Reading....................................................................................................548 15.7.5 Scope of Local Modules..............................................................................................548 15.7.6 Spruce Up Your Code with Local Modules!...............................................................548 ...........................................................................................................................................................................549 15.8 Module Overloading....................................................................................................................549 15.8.1 Overloading in PL/SQL Built−Ins...............................................................................549 15.8.2 Benefits of Overloading...............................................................................................550 15.8.3 Where to Overload Modules........................................................................................550 xiv [Appendix A] What's on the Companion Disk? Table of Contents 15.8.4 Restrictions on Overloading........................................................................................551 ...........................................................................................................................................................................554 15.9 Forward Declarations...................................................................................................................554 ...........................................................................................................................................................................556 15.10 Go Forth and Modularize!.........................................................................................................556 ...........................................................................................................................................................................557 16. Packages.....................................................................................................................................................558 16.1 The Benefits of Packages.............................................................................................................559 16.1.1 Enforced Information Hiding .......................................................................................559 16.1.2 Object−Oriented Design..............................................................................................559 16.1.3 Top−Down Design .......................................................................................................559 16.1.4 Object Persistence........................................................................................................559 16.1.5 Performance Improvement..........................................................................................560 ...........................................................................................................................................................................561 16.2 Overview of Package Structure...................................................................................................561 16.2.1 The Specification.........................................................................................................561 16.2.2 The Body ......................................................................................................................562 16.2.3 Package Syntax............................................................................................................562 16.2.4 Public and Private Package Elements..........................................................................563 16.2.5 How to Reference Package Elements..........................................................................564 16.2.6 Quick Tour of a Package.............................................................................................565 ...........................................................................................................................................................................569 16.3 The Package Specification...........................................................................................................569 16.3.1 Packages Without Bodies............................................................................................570 16.3.2 Declaring Package Cursors..........................................................................................573 ...........................................................................................................................................................................575 16.4 The Package Body.......................................................................................................................575 16.4.1 Declare in Specification or Body.................................................................................575 16.4.2 Synchronize Body with Package.................................................................................576 ...........................................................................................................................................................................578 16.5 Package Data ................................................................................................................................578 16.5.1 Architecture of Package−Based Data..........................................................................578 16.5.2 Global Within a Single Oracle Session ........................................................................579 16.5.3 Global Public Data.......................................................................................................579 16.5.4 Global Private Data ......................................................................................................580 16.5.5 Providing an Interface to Global Data.........................................................................581 ...........................................................................................................................................................................583 16.6 Package Initialization...................................................................................................................583 16.6.1 Drawbacks of Package Initialization...........................................................................583 16.6.2 Use Initialization Section for Complex Logic.............................................................583 16.6.3 Side Effects..................................................................................................................584 16.6.4 Load Session Data in Initialization Section.................................................................584 ...........................................................................................................................................................................586 17. Calling PL/SQL Functions in SQL ..........................................................................................................587 17.1 Looking at the Problem ................................................................................................................587 ...........................................................................................................................................................................590 17.2 Syntax for Calling Stored Functions in SQL...............................................................................590 ...........................................................................................................................................................................592 xv [Appendix A] What's on the Companion Disk? Table of Contents 17.3 Requirements for Stored Functions in SQL.................................................................................592 ...........................................................................................................................................................................594 17.4 Restrictions on PL/SQL Functions in SQL ..................................................................................594 ...........................................................................................................................................................................596 17.5 Calling Packaged Functions in SQL............................................................................................596 17.5.1 The RESTRICT_REFERENCES Pragma...................................................................596 17.5.2 Asserting Purity Level with Package Initialization Section........................................598 ...........................................................................................................................................................................600 17.6 Column/Function Name Precedence ............................................................................................600 ...........................................................................................................................................................................601 17.7 Realities: Calling PL/SQL Functions in SQL..............................................................................601 17.7.1 Manual Application of Pragmas..................................................................................601 17.7.2 Read Consistency Model Complications.....................................................................602 ...........................................................................................................................................................................604 17.8 Examples of Embedded PL/SQL.................................................................................................604 17.8.1 Encapsulating Calculations..........................................................................................604 17.8.2 Combining Scalar and Aggregate Values....................................................................605 17.8.3 Replacing Correlated Subqueries .................................................................................607 17.8.4 Replacing DECODEs with IF Statements...................................................................609 17.8.5 GROUP BY Partial Column Values............................................................................611 17.8.6 Sequential Processing Against a Column's Value.......................................................612 17.8.7 Recursive Processing in a SQL Statement ..................................................................613 . ...........................................................................................................................................................................616 18. Object Types..............................................................................................................................................617 18.1 Introduction to Oracle8 Objects...................................................................................................618 18.1.1 Terminology .................................................................................................................618 18.1.2 Some Simple Examples...............................................................................................619 18.1.3 Comparison: Oracle8 Objects and Earlier Features .....................................................620 18.1.4 Characteristics of Objects............................................................................................621 18.1.5 Object Programming Themes......................................................................................623 ...........................................................................................................................................................................627 18.2 Oracle Objects Example..............................................................................................................627 18.2.1 Defining the Object Type Specification......................................................................627 18.2.2 Defining the Object Type Body...................................................................................627 18.2.3 Adding Complex Data Structures................................................................................631 ...........................................................................................................................................................................634 18.3 Syntax for Creating Object Types ................................................................................................634 18.3.1 About Object Types.....................................................................................................634 18.3.2 CREATE TYPE and DROP TYPE: Creating and Dropping Types ............................634 18.3.3 CREATE TYPE BODY: Creating a Body..................................................................636 18.3.4 Dot Notation................................................................................................................636 18.3.5 SELF: The Implied Parameter.....................................................................................639 18.3.6 Comparing Objects......................................................................................................640 18.3.7 Privileges.....................................................................................................................643 ...........................................................................................................................................................................645 18.4 Manipulating Objects in PL/SQL and SQL.................................................................................645 18.4.1 The Need to Initialize..................................................................................................645 18.4.2 OID, VALUE, REF, and DEREF................................................................................647 ...........................................................................................................................................................................655 xvi [Appendix A] What's on the Companion Disk? Table of Contents 18.5 Modifying Persistent Objects .......................................................................................................655 18.5.1 Approach 1: Permit Full Use of Conventional SQL....................................................656 18.5.2 Approach 2: Define Methods and Permit Limited Use of Conventional SQL............657 18.5.3 Approach 3: Do Everything via Methods....................................................................658 18.5.4 Approach 4: Use an Object and a PL/SQL Container Package...................................664 18.5.5 Implications for Developer/2000.................................................................................667 ...........................................................................................................................................................................668 18.6 Object Housekeeping...................................................................................................................668 18.6.1 Data Dictionary............................................................................................................668 18.6.2 SQL*Plus "Describe" Command.................................................................................669 18.6.3 Schema Evolution........................................................................................................669 ...........................................................................................................................................................................672 18.7 Making the Objects Option Work................................................................................................672 ...........................................................................................................................................................................674 19. Nested Tables and VARRAYs.................................................................................................................675 19.1 Types of Collections....................................................................................................................675 ...........................................................................................................................................................................680 19.2 Creating the New Collections......................................................................................................680 19.2.1 Collections "In the Database"......................................................................................680 19.2.2 Collections in PL/SQL.................................................................................................682 ...........................................................................................................................................................................687 19.3 Syntax for Declaring Collection Datatypes.................................................................................687 ...........................................................................................................................................................................689 19.4 Using Collections.........................................................................................................................689 19.4.1 Initializing Collection Variables..................................................................................689 19.4.2 Assigning Values to Elements: Index (Subscript) Considerations..............................693 19.4.3 Adding and Removing Elements.................................................................................693 19.4.4 Comparing Collections................................................................................................695 ...........................................................................................................................................................................697 19.5 Collection Pseudo−Functions......................................................................................................697 19.5.1 The THE Pseudo−function..........................................................................................697 19.5.2 The CAST Pseudo−function........................................................................................699 19.5.3 The MULTISET Pseudo−function..............................................................................700 19.5.4 The TABLE Pseudo−function.....................................................................................702 ...........................................................................................................................................................................704 19.6 Collection Built−Ins .....................................................................................................................704 19.6.1 COUNT ........................................................................................................................705 19.6.2 DELETE [ ( i [ , j ] ) ]..................................................................................................705 19.6.3 EXISTS(i)....................................................................................................................706 19.6.4 EXTEND [ (n [,i] ) ]....................................................................................................706 19.6.5 FIRST, LAST ...............................................................................................................707 19.6.6 LIMIT..........................................................................................................................707 19.6.7 PRIOR(i), NEXT(i).....................................................................................................708 19.6.8 TRIM [ (n ) ]................................................................................................................708 ...........................................................................................................................................................................710 19.7 Example: PL/SQL−to−Server Integration...................................................................................710 ...........................................................................................................................................................................713 19.8 Collections Housekeeping...........................................................................................................713 19.8.1 Privileges.....................................................................................................................713 19.8.2 Data Dictionary............................................................................................................713 19.8.3 Call by Reference or Call by Value.............................................................................714 ...........................................................................................................................................................................715 xvii [Appendix A] What's on the Companion Disk? Table of Contents 19.9 Which Collection Type Should I Use?........................................................................................715 20.1 Example: Using Object Views.....................................................................................................716 ...........................................................................................................................................................................717 20. Object Views..............................................................................................................................................718 ...........................................................................................................................................................................723 20.2 INSTEAD OF Triggers................................................................................................................723 20.2.1 INSTEAD OF Triggers: To Use or Not to Use?.........................................................724 ...........................................................................................................................................................................727 20.3 Syntax for Object Views..............................................................................................................727 20.3.1 CREATE VIEW: Creating an Object View................................................................727 20.3.2 DROP: Dropping Views and Triggers.........................................................................728 20.3.3 MAKE_REF: Returning a Virtual REF.......................................................................728 ...........................................................................................................................................................................730 20.4 Differences Between Object Views and Object Tables...............................................................730 20.4.1 OID Uniqueness ...........................................................................................................730 20.4.2 Using REFs with Object Views...................................................................................732 20.4.3 Storage of Virtual REFs ...............................................................................................737 20.4.4 REFs to Nonunique OIDs............................................................................................737 ...........................................................................................................................................................................738 20.5 Not All Views with Objects Are Object Views...........................................................................738 ...........................................................................................................................................................................739 20.6 Schema Evolution........................................................................................................................739 ...........................................................................................................................................................................741 20.7 Object Views Housekeeping........................................................................................................741 20.7.1 Data Dictionary............................................................................................................741 20.7.2 Privileges.....................................................................................................................742 20.7.3 Forcing Compilation....................................................................................................742 ...........................................................................................................................................................................743 20.8 Postscript: Using the BFILE Datatype .........................................................................................743 ...........................................................................................................................................................................746 21. External Procedures.................................................................................................................................747 21.1 Introduction to External Procedures............................................................................................748 21.1.1 Example: Determining Free Disk Space on Windows NT..........................................748 21.1.2 Architecture.................................................................................................................750 21.1.3 Advantages ...................................................................................................................750 21.1.4 Limitations...................................................................................................................751 ...........................................................................................................................................................................753 21.2 Steps in Creating an External Procedure.....................................................................................753 21.2.1 Step 1: Set Up the Listener..........................................................................................753 21.2.2 Step 2: Identify or Create the Shared Library..............................................................755 21.2.3 Step 3: Issue CREATE LIBRARY Statement.............................................................755 21.2.4 Step 4: Create the PL/SQL Body.................................................................................756 21.2.5 Using the rand External Procedure..............................................................................757 ...........................................................................................................................................................................759 21.3 Syntax for External Procedures...................................................................................................759 21.3.1 CREATE LIBRARY: Creating the External Procedure Library.................................759 21.3.2 EXTERNAL: Creating the PL/SQL Body ...................................................................760 21.3.3 DROP: Dropping Libraries..........................................................................................761 ..................................................