Chap01-DB and Models-Oracle History

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Chap01-DB and Models-Oracle History Powered By Docstoc
					                          Database


Meaning: Data (data) Base (place where data is placed)
Organized collection of data so that data items can easily be accessed and
manipulated.

Conventional Database (Flat File System):
Information is stored in text files, data items are separated by
delimiter/space.

----     -----    -----     -----    --------------     ---------
----     -----    -----     -----    --------------     ---------
----     -----    -----     -----    --------------     ---------
Disadvantages of File Processing
Program-Data Dependence
  –All programs maintain metadata for each file they use

Data    Redundancy (Duplication of data)
  –Different systems/programs have separate copies of the same
  data
Limited    Data Sharing
  –No centralized control of data

Lengthy    Development Times
  –Programmers must design their own file formats

Excessive    Program Maintenance
         SOLUTION:
   The DATABASE Approach
• Central repository of shared data
• Data is managed by a controlling
  agent
• Stored in a standardized, convenient
  form
Database Management System
• A DBMS is a data storage and retrieval
  system which permits data to be stored
  non-redundantly while making it appear to
  the user as if the data is well-integrated.
Database Management System
    Application
        #1
•

    Application
        #2

                     DBMS                              Database
                                                      containing
                                                      centralized
                                                      shared data

     Application
         #3        DBMS manages data resources like
                   an operating system manages
                   hardware resources
       Advantages of Database
             Approach
• Program-Data Independence
    – Metadata stored in DBMS, so applications don’t need
      to worry about data formats
    – Data queries/updates managed by DBMS so
      programs don’t need to process data access routines
    – Results in: increased application development and
      maintenance productivity
• Minimal Data Redundancy
    – Leads to increased data integrity/consistency
•
      Advantages of Database
            Approach
• Improved Data Sharing
  – Different users get different views of the data
• Enforcement of Standards
  – All data access is done in the same way
• Improved Data Quality
  – Constraints, data validation rules
• Better Data Accessibility/ Responsiveness
  – Use of standard data query language (SQL)
• Security, Backup/Recovery, Concurrency
  – Disaster recovery is easier
            Costs of the
         Database Approach
• Up-front costs:
  – Installation Management Cost and Complexity
  – Conversion Costs
• Ongoing Costs
  – Requires New, Specialized Personnel
  – Need for Explicit Backup and Recovery
• Organizational Conflict
  – Old habits die hard
          The Range of
      Database Applications
• Personal Database – standalone desktop
  database
• Workgroup Database – local area network
  (<25 users)
• Department Database – local area
  network (25-100 users)
• Enterprise Database – wide-area network
  (hundreds or thousands of users)
       Evolution of DB Systems
•   Flat files - 1960s - 1980s
•   Hierarchical – 1970s - 1990s
•   Network – 1970s - 1990s
•   Relational – 1980s - present
•   Data warehousing – 1980s - present
•   Web-enabled – 1990s - present
          DataBase Model
• A Database Model defines how data can
  be stored and manipulated within a
  database.
• We would discuss three different data
  models. These Data models differ in the
  way they allow users to view and
  manipulate relationships between entities.
    DataBase Model(Historical
          Perspective)
•
          Hierarchical data Model
• Database management systems were first defined in the
  1960s to provide a common organizational framework for
  what had been data stored in independent files.
• The North American Aviation's Space Division and IBM
  developed an approach based on a hierarchical model in 1965.
• This model has a parent-child structure that is similar to an
  inverted tree, which is what forms the hierarchy. A parent
  table can have many child tables, but a child table can have
  only one parent table.
• This Data Model is considered unsuitable for its inflexible
  structure and lack of support for complex relationships
• Only one to many relationship between record is allowed(a
  purchase order is owned by only one customer) .
       Hierarchical data Model
• A hierarchical database expects the
  hierarchical tables to be defined at design-
  time and does not expect them to be
  changed during run-time. The most
  recognized and used hierarchical
  database is IMS developed by IBM.
The Hierarchical Data Model
structures data in a tree of records, with each record having one parent
record and many children. It can be represented as follows:
        Network data Model
• In 1964, Charles Bachman of General
  Electric proposed a network model with
  data records linked together. This work
  formed the basis of the CODASYL
  (Conference on Data System Languages)
  Data Base Task Group which farmed it
  into standard specification in 1969
       Network Data Model
• The Network Data Model uses a structure
  in which a record can have many parents
  as well as many children. It can be
  represented as follows:
   Deficiencies in Hierarchical and
         Network Databases
• Access to the database was not via SQL query strings,
  but by a specific set of API's, typically for FIND,
  CREATE, READ, UPDATE and DELETE.
• Each API would only access a single table (dataset), so
  it was not possible to implement a JOIN which would
  return data from several tables.
• It was not possible to provide a variable WHERE clause.
  The only selection mechanism available was
   – read all entries (a full table scan).
   – read a single entry using a specific primary key.
   – read all entries on a child table which were associated with a
     selected entry on a parent table
   Deficiencies in Hierarchical and
         Network Databases
• Any further filtering had to be done within the application
  code.
• It was not possible to provide an ORDER BY clause.
  Data was presented in the order in which it existed in the
  database. This mechanism could be tuned by specifying
  sort criteria to be used when each record was inserted,
  but this had several disadvantages:
• Only a single sort sequence could be defined for each
  path (link to a parent), so all records retrieved on that
  path would be provided in that sequence.
• It could make inserts rather slow when attempting to
  insert into the middle of a large collection, or where a
  table had multiple paths each with its own set of sort
  criteria.
         Relational Data Model
In 1970 the relational data model was defined by E.F. Codd
   (see "A Relational Model of Data for Large Shared Data
   Banks" (June 6, 1970), 377-387).
In 1974 IBM started a project called System/R to prove the
   theory of relational databases. This led to the
   development of a query language called SEQUEL
   (Structured English Query Language) later renamed
   to Structured Query Language (SQL) and now the
   query language of all databases.
Provide solution to all these previously mentioned
  Problems.
        Relational Data Model
• What is Relation???
• Relation (table) is a two-dimensional table.
• Attribute (i.e. field or data item) is a column in
  the table.
• Each column in the table has a unique name
  within that table.
• Each column is homogeneous.
• Each column has a domain .
• A Tuple (i.e. record) is a row in the table.
Relational Data Model
       Relational Data Model
• The order of the rows and columns is not
  important.
• Values of a row all relate to some thing or
  portion of a thing.
• Duplicate rows are not allowed

• A relation may be expressed using the
  notation R(A,B,C, ...)
                   Primary Key
  A primary key is a column or set of columns which is
 selected as the principal unique identifier. Every relation
must contain a primary key. The primary key is usually the
   key selected to identify a row when the database is
physically implemented. For example, Student number is
            selected instead of Student Name.
                 • Foreign Key
• A foreign key is an attribute (or set of
  attributes) that appears (usually) as a non
  key attribute in one relation and as a
  primary key attribute in another relation.
             History Of Oracle
• June 16, 1977: Software Development Laboratories
  (SDL) founded.
• June 1979: SDL renamed to "Relational Software Inc."
  (RSI). Oracle 2, the first version of the Oracle database
  software, used by Wright-Patterson Air Force Base, runs
  on PDP-11 hardware.
• March 1983: RSI rewrites Oracle in C for portability and
  releases Oracle version 3. RSI takes the name "Oracle"
  in order to align more closely with its primary product.
• October 1984: Oracle version 4 released
• November 1984: Oracle database software ported to the
  PC platform.
• April 1985: Oracle version 5 released
             History Of Oracle
• 1988: Oracle version 6 released
• June 1992: Oracle 7 released with performance
  enhancements, administrative utilities.
• June 1997: Oracle 8 released
• September 1998: Oracle 8i released
• 2000: Oracle 9i released.
 2004: Oracle 10g released.
• 2007: Oracle 11g released.
    History of Relational DataBase

•

				
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