Question

define primary key .Why do we need a primary key

Answer 1

A primary key is a special relational database table column (or combination of columns) designated to uniquely identify all table records.

A primary key’s main features are:

It must contain a unique value for each row of data.
It cannot contain null values.
A primary key is either an existing table column or a column that is specifically generated by the database according to a defined sequence.

Answer 2

Explanation:

A PRIMARY KEY is a key that differentiates the records in a file.

we need the PRIMARY KEY because PRIMARY KEY is a toggle key.