Question

what is primary key ?how it is different from other fields in the table?​

Answer 1

Explanation:

There can be one primary key in a table while there can be multiple unique keys in the table. The purpose of the primary key is to enforce entity integrity on the other hand the purpose of unique key is to enforce unique data. Primary key does not allow null columns whereas unique allows null columns.

Answer 2

Answer:

There can be one primary key in a table while there can be multiple unique keys in the table. The purpose of the primary key is to enforce entity integrity on the other hand the purpose of unique key is to enforce unique data. Primary key does not allow null columns whereas unique allows null columns.