Integrity constraints means..? how many and what are they?
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Answer Posted / firoz basha
Integrity constraint:- An IC is one which does not allow
invalid data entry into the database.
there are 3 types of Integrity constraints:
1. Entity Integrity COnstraint
primary key
unique key
Primary key does not allow null values and duplicate
values
unique key does not allow duplicate values.
unique key allows any number of null values (in case
of oracle)
unikey key allows only one null value. i.e, single null
value ( in the case of sql server 2000)
2. Domain Integrity Constraint
not null constraint
check constraint
rule constraint (in case of SQL SERVER 2000)
rule is an alternate to check constraint
3. Referential Integrity constraint
foreign key constraint
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