Question

Differentiate Unique and Primary Key constraint.

Answer 1

Unique Key Constraint	Primary Key Constraint
The constraint ensures that no two rows have the same value in the specified columns.	This constraint declares a field as a Primary Key which helps to uniquely identify a record.
The UNIQUE constraint can be applied only to fields that have also been declared as NOT NULL.	The Primary Key does not allow NULL values and therefore a field declared as Primary Key must have the NOT NULL constraint.