What is the difference b/w Primary Key and Unique Key

Question

I tried to find it out in google but not satisfactory answer is given out there. Can anybody explain the solid difference.

actually if Primary key is used to sele

Answer 1

A primary key is a unique key. Both types of key serve to uniquely identify a single row in a table. Many RDBMSs require that one of the unique keys on a table be designated as the "primary key", for several different implementation reasons. In terms of data integrity, there is no difference.