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Integrity Constraints

RGPV: DBMS: Unit 2
 
INTEGRITY CONSTRAINT
 
Integrity Constraint:-
It is the mechanism or condition used to prevent invalid data entry into the relation (table). It applies rules on the table.
Three types of integrity contraints are-
<![if !supportLists]> (1)   <![endif]> Domain integrity constraint :- Set a range on any relation that will prevent the user from performing any invalid manipulation.
They are of two types:-
 
<![if !supportLists]> (i)                 <![endif]> NOT NULL: Not allow null values
<![if !supportLists]> (ii)               <![endif]> CHECK:  Specify condition that each tuple must satisfy.
 
<![if !supportLists]> (2)   <![endif]> Entity Integrity Constraints: Applies on relation or table.
They are of two types:
 
<![if !supportLists]> (i)                 <![endif]> UNIQUE: Prevent duplicate values, allow NULL values
<![if !supportLists]> (ii)               <![endif]> PRIMARY KEY: Prevent duplicate values, don’t allow null values
 
<![if !supportLists]> (3)   <![endif]> Referential Integrity Constraint: Applies condition in two tables.
 
<![if !supportLists]> (i)                 <![endif]> FOREING KEY: Tuples in the referencing relation R1 have attribute (Foreign key attribute) that reference the primary key attribute of the referenced relation R2.
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