Database Management System ppt

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Submitted By:
Odisha Electronics Control Library
Seminar
On
Database
Management System

Content
 What is Database Management System?
 Brief History
 Why Use a DBMS?
 Purpose of DBMS
 Data models
 Architecture of DBMS
 levels or layers of DBMS architecture
 Components of DBMS
 Advantage of DBMS
 Disadvantage of DBMS
 DBMS Languages
 References

What is Database Management
System?
A Database Management System (DBMS), or simply a Database
System (DBS) consist of :
 A collection of interrelated and persistent data (usually referred
to as the database (DB)).
 A set of application programs used to access, update and
manage that data (which form the data management system
(MS)).

Brief History
 Early 1960s: first general purpose database by Charles
Bachman from GE. Used the network data model.
 Late 1960s: IBM developed Information Management System
(IMS). Used the hierarchical data model. Led to SABRE, the
airline reservation system developed by AA and IBM. Still in
use today.
 1970: Edgar Code of IBM developed the relational data model.
Led to several DBMS based on relational model, as well as
important theoretical results. Code wins Turing award.
 1980s: relational model dominant. SQL standard.
 Late 1980s, 1990s: DBMS vendors extend systems, allowing
more complex data types (images, text).

Why Use a DBMS?
 Data independence and efficient access.
 Reduced application development time.
 Data integrity and security.
 Uniform data administration.
 Concurrent access, recovery from crashes.

Purpose of DBMS
1. Data redundancy and inconsistency
 Same information may be duplicated in several places.
 All copies may not be updated properly.
2. Difficulty in new program to carry out each new task
3. Data isolation —
 Data in different formats.
 Difficult to write new application programs.
 files and formats

Purpose of DBMS …
Security problems
Every user of the system should be able to access only the data
they are permitted to see.
 E.g. payroll people only handle employee records, and cannot
see customer accounts; tellers only access account data and
cannot see payroll data.
 Difficult to enforce this with application programs.
Integrity problems
 Data may be required to satisfy constraints.
 E.g. no account balance below $25.00.
 Again, difficult to enforce or to change constraints with the
file-processing approach.

Data models
Hierarchical Model
 The hierarchical data model organizes data in a tree structure.
There is a hierarchy of parent and child data segments. This
structure implies that a record can have repeating information,
generally in the child data segments.
 Hierarchical DBMSs were popular from the late 1960s, with the
introduction of IBM's Information Management System (IMS)
DBMS, through the 1970s.

Network Model
 The popularity of the network data model coincided with the
popularity of the hierarchical data model. Some data were
more naturally modeled with more than one parent per child.
 So, the network model permitted the modeling of many-to-
many relationships in data. In 1971, the Conference on Data
Systems Languages (CODASYL) formally defined the
network model.

Relational Model
 (RDBMS - relational database management system) A
database based on the relational model developed by E.F.
Code.
 A relational database allows the definition of data structures,
storage and retrieval operations and integrity constraints.
 In such a database the data and relations between them are
organized in tables. A table is a collection of records and each
record in a table contains the same fields.

Properties of Relational Tables
 Values Are Atomic
 Each Row is Unique
 Column Values Are of the Same Kind
 The Sequence of Columns is Insignificant
 The Sequence of Rows is Insignificant
 Each Column Has a Unique Name

Object-Oriented Model
 Object DBMSs add database functionality to object
programming languages. They bring much more than
persistent storage of programming language objects.
 A major benefit of this approach is the unification of the
application and database development into a seamless data
model and language environment.

Semi structured Model
 In semi structured data model, the information that is normally
associated with a schema is contained within the data, which
is sometimes called ``self-describing''.
 In such database there is no clear separation between the data
and the schema, and the degree to which it is structured
depends on the application.

Architecture of DBMS
 An early proposal for a standard terminology and general
architecture database a system was produced in 1971 by the
DBTG (Data Base Task Group) appointed by the Conference
on data Systems and Languages.
 The DBTG recognized the need for a two level approach with
a system view called the schema and user view called
subschema. The American National Standard Institute
terminology and architecture in 1975.ANSI-SPARC
recognized the need for a three level approach with a system
catalog.
There are following three levels or layers of DBMS
architecture:
 1. External Level
 2. Conceptual Level
 3. Internal Level

levels or layers of DBMS
architecture
 External Level: - External Level is described by a schema i.e.
it consists of definition of logical records and relationship in
the external view.
 Conceptual Level: - Conceptual Level represents the entire
database. Conceptual schema describes the records and
relationship included in the Conceptual view. .
 Internal Level: - Internal level indicates hoe the data will be
stored and described the data structures and access method to
be used by the database.

Components of DBMS
1. Hardware: Can range from a PC to a network of
computers.
2. Software: DBMS, operating system, network software (if
necessary) and also the application programs.
3. Data: Used by the organization and a description of this
data called the schema.
4. People: Includes database designers, DBAs, application
programmers, and end-users.
5. Procedure: Instructions and rules that should be applied
to the design and use of the database and DBMS.

Advantage of DBMS
 Controlling Redundancy
 Sharing of Data
 Data Consistency
 Integration of Data
 Integration Constraints
 Data Security
 Report Writers

Advantage of DBMS…
 Control Over Concurrency
 Backup and Recovery Procedures
 Data Independence

Disadvantage of DBMS
 Cost of Hardware and Software
 Cost of Data Conversion
 Cost of Staff Training
 Appointing Technical Staff
 Database Damage

DBMS Languages
Data Definition Language-DDL
 Data Definition Language (DDL) statements are used to
define the database structure or schema.
Some examples:
 CREATE - to create objects in the database
 ALTER - alters the structure of the database
 DROP - delete objects from the database
 TRUNCATE - remove all records from a table, including all
spaces allocated for the records are removed
 COMMENT - add comments to the data dictionary
 RENAME - rename an object

Data Manipulation Language
(DML)
Data Manipulation Language (DML) statements are used for
managing data within schema objects.
Some examples:
 SELECT - Retrieve data from the a database
 INSERT - Insert data into a table
 UPDATE - Updates existing data within a table
 DELETE - deletes all records from a table, the space for the
records remain
 MERGE - UPSERT operation (insert or update)
 CALL - Call a PL/SQL or Java subprogram
 EXPLAIN PLAN - explain access path to data
 LOCK TABLE - control concurrency

Thanks….!!!!!!!
 Any Query….!!!!!!!

Database Management System ppt

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Database Management System ppt