Question

What is the importance of a primary key in a table ? Explain with a suitable example.

Answer 1

A primary key is a set of one or more attributes that can uniquely identify tuples within the relation.

For example, in the following table ITEM, the column Ino can uniquely identify each row in the table, hence Ino is the primary key of the following table.

Ino	Item	Quantity
1	Pen	220
2	CD	530
3	DVD	450
4	Duster	110