Data base management system

2. i. What is DBMS ? Data Items & Records.
ii.Reasons for using DBMS?

3. What is DBMS?
o A Data Base Management System is a collection of logically
related data files as well as programs required to manage
that data.
o It is a computerized record-keeping system. It maintain
data and provide it to user when required.
o Example:
A bank DBMS may have separate files for the
clients as follows:
• Saving Accounts
• Current Accounts & clients information etc.

4. Components Of
DBMS :
1- Data:
• Data is a collection of
facts/figures stored in the
database.
2- Hardware:
The physical components of a
computer system.
Example:
• Secondary Storage & Main Memory.
• I/O devices & Processors.

5. Components Of DBMS :
3- Software:
• Software is a collection of programs used by computer
within a database system.
• DBMS uses three types of software to enable the
database system work properly.
i. OS Software:
Itmanages all hardware components &software to run
on computer.
ii. DBMS Software:
Itmanages the database in database system.

6. Components Of DBMS :
iii.Application Programs:
• These are used to access &process the data stored in the
database.
4- Personnel :-
The people related to database system are called
personnel. They are as follows:
 Database Administrators:
They are responsible of the whole database system. They
authorize access to database and monitor the use &working
of database system.
 Application Programmers:
They write application programs to access data from
database.

7. Components Of DBMS :
 End Users:
These peoples use application programs to perform
different task on database. They include clerks , managers ,
directors etc.
Hierarchy Of Data in DBMS:
o Data in database is classified in a hierarchy.
o A database contains files>records>fields>characters.
 Field:
• A combination of one or more characters.
• Field data type: Indicates type of data in field.
• Field Size: Defines maximum no of characters in a field.

8. Hierarchy Of Data in DBMS:
 Record:
• A collection of related fields
treated as single unit.
Example:
Employee’s record.
 File:
• A collection of related records
treated as single unit.
• Files are stored on stored on
storage media like Hard Disk
etc.

9. KEYS:
Primary Key:
• An attribute or set of attributes that
uniquely identifies a row or record in a
relation/table is known as primary key.
• A relation can have only one Primary Key.
• Each value in Primary Key attribute must be
unique.
• Primary Key cannot contain null values.
 Candidate Key:
• The attributes or set of attributes that can
be used as primary key is called
Candidate Key.
Reg No Name Class
10 Asad C.A
20 Mohsin P.H.D
30 Zeeshan M.B.B.S
The attribute Reg No is Primary
Key.

10. KEYS:
 Alternate Key:
• The candidate keys
that are not selected
as primary key are
know as Alternate
Keys.
 Composite Key:
• A primary key that
consists of two or
more attributes is
known as Composite
Key.

11. KEYS:
 Secondary Key:
• An attribute or set of
attributes that is bases for
retrieval is called S.K
• One Secondary Key value
may refer to many records.
• Secondary Key can be a
non-unique attribute.
 Foreign Key:
• A Foreign Key is an
attribute or set of
attributes in a
relation/table whose
values match a
primary key in another
relation.

12. KEYS:
 Sort/Control Key:
• An attribute or set of attributes that is used to physically
sequence the stored data is called sort/control key.
Facilities Of DBMS:
 Adding new files to database.
 Inserting new data in existing files.
 Retrieving data from existing files.
 Updating data in existing files.
 Deleting data from existing files.
 Removing existing files from database.