Database Management System ppt

www.oeclib.in 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