Database Constraints
Constraints are the rules which are applied to a table to filter out data
during insert or update operations. Constraints can be added at the time of
creating a table or altering a table. Constraints are the conditions which
should be satisfied by insert or update query. There are 2 types of constraints:
1)
Input output (I/O) constraints:
a.
These are of following types:
i.
Primary Key
ii.
Foreign Key
iii.
Unique Key
2)
Check (Business Rules) constraints:
a.
These are defined at 2 levels
i.
Table Level
ii.
Column Level
