Saturday, 3 December 2016

Introduction of DBMS Part-2

Data Independence in DBMS:
Upper level are unaffected by changes in lower level.

Two Types of Data Independence:

a)Physical Data Independence:

  • Physical storage structure or devices can be changed without affecting conceptual schema.
  • Modification done to improve performance.
  • It provide independence to conceptual schema and external schema

b)Logical Data Independence:

  • Conceptual schema can be changed without affecting external schema.
  • Structure of database is altered when modification done in conceptual schema.
  • It provide independence to external schema.

DBMS Components:

  • Processor/main memory(used for execution)
  • Secondary Storage devices(for physical storage)

5)Procedures(Set of rules for database management)

Types of Users:

a)Naive Users:
End Users of the database who work through menu driven application programs, where the type and range of response is always indicated to the users.

b)Online Users:
Those users who may communicate with database directly through an online terminal.

c)Application Programmer:
Those users who are responsible for developing the application program.

d)DBA(Database Administrator)

DBA(Database Administrator):
DBA directs or performs all activities related to maintaining a successful database environment.

Function of DBA:

  • Defining Conceptual Schema
  • Physical Database Design
  • Tuning database performance
  • Security and Integrity Check
  • Back up and Recovery Strategies
  • Improving query processing performance
  • Granting User Access

Database Languages:

1)DDL(Data Definition Language):

  • Deals with database schemas and description, how the data should reside in the database.
  • Used to alter/modify a database or table structure and schema.

Command used in DDL:

  • Create
  • Alter
  • Drop
  • Rename
  • Truncate
  • Comment

2)DML(Data Manipulation Language)

  • Deals with data manipulation
  • These statements afffects records in a table.

Command used in DML:

  • Update
  • Select
  • Insert
  • Delete
  • Merge
  • Call
  • Lock Table

Two Types of DML:
a)Procedural DML(How data is fetch)
b)Non-Procedural DML(What data is to be fetch)

3)DCL(Data Control Language)
Control the level of access that users have on database objects.
Command used in DCL:

  • Grant 
  • Revoke

4)Transaction Language:
Control and manage transactions to maintain integrity of data within SQL statement.
Command used in Transaction Language:

  • Set Transaction
  • Commit
  • Savepoint
  • Rollback

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