Question

What is a primary key?​

Answer 1

Answer:

In the relational model of databases, a primary key is a specific choice of a minimal set of attributes that uniquely specify a tuple in a relation. Informally, a primary key is "which attributes identify a record", and in simple cases are simply a single attribute: a unique id.

Answer 2

In the rational model of databases, a primary key is a specific choice of a minimal set of attributes that uniquely specify a tuple in a relation. informally ,a primary key is"which attributes identify record ",and in simple cases are simply a single attributes : a unique id.