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:
1)Hardware

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

2)Data
3)Software
4)Users
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