Answer / chandonline

Basic difference between primary key and unique is that primary key is used to define a table in other tables for preventing data from anomalies,and unique key is used in a table to apply unifications among different values or columns of a tables and only in that table obviously.Their is no usage of unique key outward a table but primary key is often used to make relations between other tables.

Answer / ashish tyagi

The basic difference between primary key and unique key is that unique key allows null value but primary key did not allow null value.

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