What are constraints? Explain different types of
constraints?
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Answer Posted / aravindu chowdary
CONSTRAINTS:
*It is a rule (or) restriction ,which is enforced during a
creation of table.
*constraints raises automatically at the time of
inertion,updation,deletion.
*constraints there are 3 types
1.Domain Integrity
* Not null:Donot allow null value.
* check: Limits the range of values or domain, checks
the values which a col can have
2.Entity Integrity
* Unique key:donot allow duplicate values, but allows
one null per col.Can have multiple unique constraints on a
table
* Primary key : Ensure no duplicate data and not allow
nulls.
3.Refrential Intrgrity
*Forgien key:Referntial integrity b/w 2 tables, one
table col values based on other table col values
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