Constraints are the Restrictions Placed either at a Column level or Table level. A Constraint ensures that the data meets certain Data integrity rules.
There are 3 types of Constraints. They are :
1. Domain Constraints
2. Entity Constraints 3. Referential Integrity Constraints
Domain Constraints Deal with One or more Columns.
Entity Constraints requires every row to have a unique value for a column or combination of columns.
Referential Integrity Constraints are created when a value in one column must match the value in another column, in the same/other table.
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