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					MySQL and Requirements

        Session 4
       INFM 718N
   Web-Enabled Databases
                Agenda

• Database normalization

• Access and MySQL

• Requirements analysis

• (if we have time) PHP-MySQL integration
• Relational normalization
• Structured programming
• Software patterns
• Object-oriented design
• Functional decomposition



                                           Client Hardware            (PC)
         Interface
          Design




                                            Web Browser               (IE, Firefox)


                                Client-side Programming               (JavaScript)
         Business Interaction
                    Design




                                               Interchange Language   (HTML, XML)

                                     Server-side Programming          (PHP)
          rules




                                              Database                (MySQL)

                                          Server Hardware             (PC, Unix)
          An E-R Example
                       manage-role
                           1

                  M                    1
        student          member-of           team
                                              1

                          M
human                 implement-role         creates

                                              1
                  1                    M
         client            needs           project

                                                  d

                               php-project             ajax-project
Making Tables from E-R Diagrams
• Pick a primary key for each entity
• Build the tables
  – One per entity
  – Plus one per M:M relationship
  – Choose terse but memorable table and field names
• Check for parsimonious representation
  – Relational “normalization”
  – Redundant storage of computable values
• Implement using a DBMS
Extended ER Diagram (Access)
     Goals of “Normalization”
• Save space
  – Save each fact only once

• More rapid updates
  – Every fact only needs to be updated once

• More rapid search
  – Finding something once is good enough

• Avoid inconsistency
  – Changing data once changes it everywhere
                    Normalization
• 1NF: Single-valued indivisible (atomic) attributes
  – Split “Doug Oard” to two attributes as (“Doug”, “Oard”)
  – Model M:M implement-role relationship with a table
• 2NF: Attributes depend on complete primary key
  – (id, impl-role, name)->(id, name)+(id, impl-role)
• 3NF: Attributes depend directly on primary key
  – (id, addr, city, state, zip)->(id, addr, zip)+(zip, city, state)
• 4NF: Divide independent M:M tables
  – (id, role, courses) -> (id, role) + (id, courses)
• 5NF: Don’t enumerate derivable combinations
      Normalized Table Structure
•   Persons: id, fname, lname, userid, password
•   Contacts: id, ctype, cstring
•   Ctlabels: ctype, string
•   Students: id, team, mrole
•   Iroles: id, irole
•   Rlabels: role, string
•   Projects: team, client, pstring
            Referential Integrity
• “Foreign key” values must exist in another table
  – If not, those records cannot be joined

• Checked when data added to this table
  – MySQL “Error 150”

• Triggers when data deleted/changed in other table
  – Specify SET NULL, RESTRICT or CASCADE
         Getting started with MySQL
• “root” creates database, grants permissions
  – By you on WAMP (mysql –u root –p)
  – By Charles Goldman on OTAL
  – CREATE DATABASE team1;
  – GRANT SELECT, INSERT, UPDATE, DELETE, INDEX, ALTER, CREATE, DROP ON
    team1.* TO ‘foo’@’localhost’ IDENTIFIED BY ‘bar’;
  – FLUSH PRIVILEGES;

• Start mysql
  – Start->Run->cmd for WAMP, ssh for OTAL
  – mysql –u foo –p bar [you can cd to your playspace first, but you don’t need to]

• Connect to your database
  – USE team1;
Some Useful MySQL Commands
• Looking around
  –   SHOW DATABASES;
  –   SHOW TABLES;
  –   DESCRIBE tablename;
  –   SELECT * FROM tablename;

• Optimization
  – SHOW TABLE STATUS \G;
      • OPTIMIZE TABLE tablename;
  – EXPLAIN <SQLquery>;
      • ALTER TABLE tablename ADD INDEX fieldname;
                  Creating Tables
CREATE TABLE contacts (
  ckey    MEDIUMINT UNSIGNED NOT NULL AUTO_INCREMENT,
  id      MEDIUMINT UNSIGNED NOT NULL,
  ctype   SMALLINT UNSIGNED NOT NULL,
  cstring VARCHAR(40) NOT NULL,
  FOREIGN KEY (id) REFERENCES persons(id) ON DELETE CASCADE,
  FOREIGN KEY (ctype) REFERENCES ctlabels(ctype) ON DELETE RESTRICT,
  PRIMARY KEY (ckey)
) ENGINE=INNODB;



To delete: DROP TABLE contacts;
              Populating Tables
INSERT INTO ctlabels
 (string) VALUES
 ('primary email'),
 ('alternate email'),
 ('home phone'),
 ('cell phone'),
 ('work phone'),
 ('AOL IM'),
 ('Yahoo Chat'),
 ('MSN Messenger'),
 (‘other’);


 To empty a table: DELETE FROM ctlabels;
    The SQL SELECT Command
• SELECT (“projection”) chooses columns
  – Based on their label

• WHERE (“restriction”) chooses rows
  – Based on their contents
     • e.g. department ID = “HIST”


• These can be specified together
  – SELECT Student ID, Dept WHERE Dept = “History”
             WHERE Clause
• Each SELECT contains a single WHERE

• Numeric comparison
  <, >, =, <>, …
     • e.g., grade<80

• Boolean operations
  – e.g., Name = “John” AND Dept <> “HIST”
        Connecting PHP to MySQL
• On WAMP:
$dbc=mysql_connect (‘localhost’, ‘userid’, ‘password’);


• On OTAL:
$dbc=mysql_connect(‘:/export/software/otal/mysql/run/mysqld.sock’,
                   ‘userid’, ‘password’);
      Using PHP with (X)HTML Forms
<form action=“formResponseDemo.php”, method=“post”>
   email: <input type=“text”, name=“email”, value=“<?php echo $email ?>”, size=30 />
   <input type=“radio”, name=“sure”, value=“yes” /> Yes
   <input type=“radio”, name=“sure”, value=“no” /> No
   <input type=“submit”, name=“submit”, value=“Submit” />
   <input type=“hidden”, name=“submitted”, value=“TRUE” />
</form>

if (isset($_POST[“submitted”])) {
     echo “Your email address is $email.”;
} else {
     echo “Error: page reached without proper form submission!”;
}
<?php # Script 8.1 - mysql_connect.php
// Set the database access information as constants.
DEFINE ('DB_USER', 'tester');
DEFINE ('DB_PASSWORD', 'tester');
DEFINE ('DB_HOST', 'localhost');
DEFINE ('DB_NAME', 'sitename');

// Make the connection.
$dbc = @mysql_connect (DB_HOST, DB_USER, DB_PASSWORD) OR die ('Could not connect to
MySQL: ' . mysql_error() );

// Select the database.
@mysql_select_db (DB_NAME) OR die ('Could not select the database: ' . mysql_error() );

// Create a function for escaping the data.
function escape_data ($data) {
              // Address Magic Quotes.
              if (ini_get('magic_quotes_gpc')) {
                            $data = stripslashes($data);
              }
              // Check for mysql_real_escape_string() support.
              if (function_exists('mysql_real_escape_string')) {
                            global $dbc; // Need the connection.
                            $data = mysql_real_escape_string (trim($data), $dbc);
              } else {
                            $data = mysql_escape_string (trim($data));
              }
              // Return the escaped value.
              return $data;
} // End of function.
?>
<?php # Script 9.15 - login.php (7th version after Scripts 9.1, 9.3, 9.6, 9.10. 9.13 & 9.14)
// Send NOTHING to the Web browser prior to the session_start() line!
// Check if the form has been submitted.

if (isset($_POST['submitted'])) {
   require_once ('../mysql_connect.php'); // Connect to the db.
   $errors = array(); // Initialize error array.

 // Check for an email address.
 if (empty($_POST['email'])) {
    $errors[] = 'You forgot to enter your email address.';
 } else {
    $e = escape_data($_POST['email']);
 }

 // Check for a password.
 if (empty($_POST['password'])) {
    $errors[] = 'You forgot to enter your password.';
 } else {
    $p = escape_data($_POST['password']);
 }
if (empty($errors)) { // If everything's OK.
      /* Retrieve the user_id and first_name for that email/password combination. */
      $query = "SELECT user_id, first_name FROM users WHERE email='$e' AND password=SHA('$p')";
      $result = @mysql_query ($query); // Run the query.
      $row = mysql_fetch_array ($result, MYSQL_NUM); // Return a record, if applicable.
      if ($row) { // A record was pulled from the database.
         // Set the session data & redirect.
         session_name ('YourVisitID');
         session_start();
         $_SESSION['user_id'] = $row[0];
         $_SESSION['first_name'] = $row[1];
         $_SESSION['agent'] = md5($_SERVER['HTTP_USER_AGENT']);
         // Redirect the user to the loggedin.php page.
         // Start defining the URL.
         $url = 'http://' . $_SERVER['HTTP_HOST'] . dirname($_SERVER['PHP_SELF']);
         // Check for a trailing slash.
         if ((substr($url, -1) == '/') OR (substr($url, -1) == '\\') ) {
            $url = substr ($url, 0, -1); // Chop off the slash.
         }
         // Add the page.
         $url .= '/loggedin.php';
         header("Location: $url");
         exit(); // Quit the script.
      } else { // No record matched the query.
         $errors[] = 'The email address and password entered do not match those on file.'; // Public message.
         $errors[] = mysql_error() . '<br /><br />Query: ' . $query; // Debugging message.
      }
   } // End of if (empty($errors)) IF.
   mysql_close(); // Close the database connection.
} else { // Form has not been submitted.
   $errors = NULL;
} // End of the main Submit conditional.
// Begin the page now.
$page_title = 'Login';
include ('./includes/header.html');

if (!empty($errors)) { // Print any error messages.
   echo '<h1 id="mainhead">Error!</h1>
   <p class="error">The following error(s) occurred:<br />';
   foreach ($errors as $msg) { // Print each error.
      echo " - $msg<br />\n";
   }
   echo '</p><p>Please try again.</p>';
}

// Create the form.
?>

<h2>Login</h2>
<form action="login.php" method="post">
  <p>Email Address: <input type="text" name="email" size="20" maxlength="40" /> </p>
  <p>Password: <input type="password" name="password" size="20" maxlength="20" /></p>
  <p><input type="submit" name="submit" value="Login" /></p>
  <input type="hidden" name="submitted" value="TRUE" />
</form>

<?php
include ('./includes/footer.html');
?>
             Arrays in PHP
• A set of key-element pairs
  $days = array(“Jan”->31, “Feb”=>28, …);
  $months = explode(“/”, “Jan/Feb/Mar/…/Dec”);
  $_POST


• Each element is accessed by the key
  – {$days[“Jan”]}
  – $months[0];

• Arrays and loops work naturally together
       Thinking about Arrays
• Naturally encodes an order among elements
  – $days = rksort($days);

• Natural data structure to use with a loop
  – Do the same thing to different data

• PHP unifies arrays and hashtables
  – Elements may be different types
              Functions in PHP
• Declaration
  function multiply($a, $b=3){return $a*$b;}

• Invoking a method
  $b = multiply($b, 7);

• All variables in a function have only local scope
  • Unless declared as global in the function
          Why Modularity?
• Limit complexity
  – Extent
  – Interaction
  – Abstraction


• Minimize duplication
      What are Requirements?
• Attributes
  – Appearance
  – Concepts (represented by data)


• Behavior
  – What it does
  – How you control it
  – How you observe the results
     Who Sets the Requirements?
• People who need the task done (customers)

• People that will operate the system (users)

• People who use the system’s outputs

• People who provide the system’s inputs

• Whoever pays for it (requirements commissioner)
   The Requirements Interview
• Focus the discussion on the task
  – Look for entities that are mentioned
• Discuss the system’s most important effects
  – Displays, reports, data storage
  – Learn where the system’s inputs come from
  – People, stored data, devices, …
• Note any data that is mentioned
  – Try to understand the structure of the data
• Shoot for the big picture, not every detail
              First Things First
• Functionality

• Content

• Usability

• Security/Stability
Backup Slides
               A Denormalized “Flat File”

Student ID Last Name   First Name   Department IDDepartmentCourse ID Course description Grades email
    1      Arrows      John         EE           EE         lbsc690 Information Technology 90 jarrows@wam
    1      Arrows      John         EE           Elec Engin ee750 Communication            95 ja_2002@yahoo
    2      Peters      Kathy        HIST         HIST       lbsc690 Informatino Technology 95 kpeters2@wam
    2      Peters      Kathy        HIST         history    hist405 American History       80 kpeters2@wma
    3      Smith       Chris        HIST         history    hist405 American History       90 smith2002@glue
    4      Smith       John         CLIS         Info Sci   lbsc690 Information Technology 98 js03@wam
A Normalized Relational Database
 Student Table
Student ID       Last Name            First Name   Department ID     email
             1   Arrows               John         EE                jarrows@wam
             2   Peters               Kathy        HIST              kpeters2@wam
             3   Smith                Chris        HIST              smith2002@glue
             4   Smith                John         CLIS              js03@wam

Department Table                              Course Table
Department ID    Department                   Course ID            Course Description
EE               Electronic Engineering       lbsc690              Information Technology
HIST             History                      ee750                Communication
CLIS             Information Stuides          hist405              American History

                 Enrollment Table
                 Student ID          Course ID                Grades
                                 1   lbsc690                                90
                                 1   ee750                                  95
                                 2   lbsc690                                95
                                 2   hist405                                80
                                 3   hist405                                90
                                 4   lbsc690                                98
                           Example of Join
Student Table                                                            Department Table
Student ID     Last Name   First Name   Department ID   email            Department ID   Department
             1 Arrows      John         EE              jarrows@wam
                                                                         EE              Electronic Engineering
             2 Peters      Kathy        HIST            kpeters2@wam
             3 Smith       Chris        HIST            smith2002@glue   HIST            History
             4 Smith       John         CLIS            js03@wam         CLIS            Information Stuides




    “Joined” Table
   Student ID Last Name    First Name       Department IDDepartment                      email
       1      Arrows       John             EE           Electronic Engineering          jarrows@wam
       2      Peters       Kathy            HIST         History                         kpeters2@wam
       3      Smith        Chris            HIST         History                         smith2002@glue
       4      Smith        John             CLIS         Information Stuides             js03@wam
                                     Project
 New Table
Student ID Last Name    First Name   Department IDDepartment               email
    1      Arrows       John         EE           Electronic Engineering   jarrows@wam
    2      Peters       Kathy        HIST         History                  kpeters2@wam
    3      Smith        Chris        HIST         History                  smith2002@glue
    4      Smith        John         CLIS         Information Stuides      js03@wam
                                SELECT Student ID, Department
                       Student ID     Department
                           1          Electronic Engineering
                           2          History
                           3          History
                           4          Information Stuides
                                Restrict
 New Table
Student ID Last Name   First Name   Department IDDepartment               email
    1      Arrows      John         EE           Electronic Engineering   jarrows@wam
    2      Peters      Kathy        HIST         History                  kpeters2@wam
    3      Smith       Chris        HIST         History                  smith2002@glue
    4      Smith       John         CLIS         Information Stuides      js03@wam

                              WHERE Department ID = “HIST”

Student ID Last Name       First Name Department IDDepartment               email
    2 Peters               Kathy      HIST         History                  kpeters2@wam
    3 Smith                Chris      HIST         History                  smith2002@glue
        Sources of Complexity

• Syntax
  – Learn to read past the syntax to see the ideas
  – Copy working examples to get the same effect


• Interaction of data and control structures
  – Structured programming


• Modularity
    Some Things to Pay Attention To
Syntax
• How layout helps reading   Modular Programming
• How variables are named    • Functional decomposition
• How strings are used       • How functions are invoked
• How input is obtained      • How arguments work
• How output is created      • How scope is managed
                             • How errors are handled
Structured Programming       • How results are passed
• How things are nested
• How arrays are used
  Programming Skills Hierarchy
• Reusing code [run the book’s programs]

• Understanding patterns [read the book]

• Applying patterns [modify programs]

• Coding without patterns [programming]

• Recognizing new patterns
            Best Practices
• Design before you build

• Focus your learning

• Program defensively

• Limit complexity

• Debug syntax from the top down
      Rapid Prototyping + Waterfall
                 Update
               Requirements
                                  Write
                               Specification
   Initial       Choose
Requirements   Functionality              Create
                                         Software

                  Build
                Prototype                        Write
                                                Test Plan
        Focus Your Learning
• Find examples that work
  – Tutorials, articles, examples


• Cut them down to focus on what you need
  – Easiest to learn with throwaway programs


• Once it works, include it in your program
  – If it fails, you have a working example to look at
      Defensive Programming
• Goal of software is to create desired output

• Programs transform input into output
  – Some inputs may yield undesired output

• Methods should enforce input assumptions
  – Guards against the user and the programmer!

• Everything should be done inside methods
         Limiting Complexity
• Single errors are usually easy to fix
  – So avoid introducing multiple errors

• Start with something that works
  – Start with an existing program if possible
  – If starting from scratch, start small

• Add one new feature
  – Preferably isolated in its own method
             Types of Errors
• Syntax errors
  – Detected at compile time

• Run time exceptions
  – Cause system-detected failures at run time

• Logic errors
  – Cause unanticipated behavior (detected by you!)

• Design errors
  – Fail to meet the need (detected by stakeholders)
      Debugging Syntax Errors
• Focus on the first error message
  – Fix one thing at a time

• The line number is where it was detected
  – It may have been caused much earlier

• Understand the cause of “warnings”
  – They may give a clue about later errors

• If all else fails, comment out large code regions
  – If it compiles, the error is in the commented part
        Run Time Exceptions
• Occur when you try to do the impossible
  – Use a null variable, divide by zero, …


• The cause is almost never where the error is
  – Why is the variable null?


• Exceptions often indicate a logic error
  – Find why it happened, not just a quick fix!
Debugging Run-Time Exceptions
• Run the program to get a stack trace
  – Where was this function called from?

• Print variable values before the failure

• Reason backwards to find the cause
  – Why do they have these values?


• If necessary, print some values further back
               Logic Errors
• Evidenced by inappropriate behavior

• Can’t be automatically detected
  – “Inappropriate” is subjective

• Sometimes very hard to detect
  – Sometimes dependent on user behavior
  – Sometimes (apparently) random

• Cause can be hard to pin down
       Debugging Logic Errors
• First, look where the bad data was created

• If that fails, print variables at key locations
   – if (DEBUG) echo “\$foobar = $foobar”;

• Examine output for unexpected patterns

• Once found, proceed as for run time errors
   – define (“DEBUG”, FALSE); to clean the output
             Three Big Ideas
• Functional decomposition
  – Outside-in design

• High-level languages
  – Structured programming, object-oriented design

• Patterns
  – Design patterns, standard algorithms, code reuse
          One-Minute Paper
What was the muddiest point in today’s class?

• Be brief!
• No names!

				
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posted:2/14/2013
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