Question

What is a PRIMARY KEY? What are the conditions to make field a primary key?

Answer 1

Answer:

A primary key is a field in a table which uniquely identifies each row/record in a database table. Primary keys must contain unique values. A primary key column cannot have NULL values. A table can have only one primary key, which may consist of single or multiple fields.

Answer 2

Answer:

The primary key is a unique identifier for a record . This field can never be blank or can contain a NULL value . The primary key is a unique value for that column and hence it cannot be the same for two records . Each table must have only one column set as primary key