Many times while executing querry suppose

 select 100/0 

it will encounter error as ..
Divide by zero error encountered.

So,as this is a simple example we can find out the error. But sometimes in long procedure it would be difficult.
SO it this case you can get the value as null insted of error by including these two steps

1.> SET ARITHABORT OFF
Description :
This is used to handle divide by zero problem .If you you will make it off .

2> SET ANSI_WARNINGS ON
ANSI_WARNINGS should be set to ON for executing distributed queries.

iF SET ARITHABORT is OFF and SET ANSI_WARNINGS is ON, SQL Server still returns an error message when encountering divide-by-zero or overflow errors.
sO YOU HAVE TO MAKE BOTH OF THEM AS OFF.........................


SO,NOW IF WE WILL TRY

SET ARITHABORT OFF SET ANSI_WARNINGS OFF
SELECT 100/0

It will return result as NULL

Hope this article will give a basic idea..