Question

Which of the following fields will not make a suitable primary key:
1) Costomer Account number
2) Adhar number
3) A salary field
4) Student admission number

Answer 1

Answer:

3) A salary field....

Because

Custom Account number will be unique to each and every customer. It can't be changed in future also.

Adhar number will be also unique to each individual person, Can't be changed in future also.

Student admission no is also unique and can't be changed in future also.

But salary field can't be unique because it need to change every time, when salary increase and decrease..