Question

what is primary key?

Answer 1

A primary key is a key in a relational database that is unique for each record. 

Answer 2

A primary key, also called a primarykeyword, is a key in a relational database that is unique for each record. It is a unique identifier, such as a driver license number, telephone number (including area code), or vehicle identification number (VIN). A relational database must always have one and only one primary key.