Question

What do you understand by Candidate Keys in a table? Give a suitable example of Candidate Keys from a table containing some meaningful data.

Answer 1

A table may have more than one such attribute/group of attributes that identifies a tuple uniquely, all such attribute(s) are known as Candidate Keys.

Table: Item

Ino	Item	Qty
I01	Pen	500
I02	Pencil	700
I04	CD	500
I09		700
I05	Eraser	300
I03	Duster	200

In the above table Item, ItemNo can be a candidate key

Comments

if itemno 109 has an item "ruler", then what are the candidate keys?