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Integrity Constraints in DBMS

Integrity Constraints

  • The Set of rules which is used to maintain the quality of information are known as integrity constraints.
  • Integrity constraints make sure about data intersection, update and so on.
  • Integrity constraints can be understood as a guard against unintentional damage to the database.

 

Different types of Integrity Constraints

 

 

Domain Constraint

  • The Definition of an applicable set of values is known as domain constraint.
  • Strings, character, time, integer, currency, date etc. Are examples of the data type of domain constraints.

Example

ID

NAME

SEMESTER

AGE

100

Jai

1st

27

101

BKadam

4th

34

102

Rajeev

3rd

31

103

Asmita

6th

29

104

Mahesh

2nd

Twenty two

‘Twenty two’ is not allowed for 104 id because the attribute AGE is an integer

 

Entity Integer Constraint

  • Entity Integrity Constraints states that the primary value key cannot be null because the primary value key is used to find out individual rows in relation and if the value of the primary key is null then it is not easy to identify those rows.
  • There can be a null value in the table apart from the primary key field.

Example

Emp_ID

Emp_Name

Salary

11

Manish

30000

12

Vikram

20000

13

Sudhir

10000

Rajeev

40000

Null is not allowed in Emp_ID as it is a Primary key and cannot have a NULL value.

 

Referential Integrity Constraint

Referential Integrity Constraint is specific between two tables.

 

 

Key Constraints

  • The Entity within its entity set is identified uniquely by the key which is the entity set.
  • There can be a number of keys in an entity set but only one will be the primary key out of all keys. In a relational table a primary key can have a unique as well as a null value.

Example

ID

NAME

SEMESTER

AGE

100

Naren

4

27

101

Lalit

6

28

102

Shivanshu

3

22

103

Navdeep

5

29

102

Karthik

7

25

All row ID must be unique hence 102 is not allowed.

 

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