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Constraints

 
* Not Null : Column does not accept NULL values.

* Unique : Column does not accept Duplicate values, accepts 1 NULL.

* Primary Key : Column does not accept Duplicate and NULL values.

* Foreign Key : Identify and enforce the relationships between Tables.

* Check : Enforce domain integrity by limiting the values that are accepted by one or more columns.

* Default : Store default value when no value is specified.