How to avoid the "divide by zero" error in SQL?

In order to avoid a "Division by zero" error we have programmed it like this:

Select Case when divisor=0 then null
Else dividend / divisor
End ,,,

But here is a much nicer way of doing it:

Select dividend / NULLIF(divisor, 0) ...

Now the only problem is to remember the NullIf bit, if I use the "/" key.

In case you want to return zero, in case a zero devision would happen, you can use:

SELECT COALESCE(dividend / NULLIF(divisor,0), 0) FROM sometable

For every divisor that is zero, you will get a zero in the result set.

This seemed to be the best fix for my situation when trying to address dividing by zero, which does happen in my data.

Suppose you want to calculate the male–female ratios for various school clubs, but you discover that the following query fails and issues a divide-by-zero error when it tries to calculate ratio for the Lord of the Rings Club, which has no women:

SELECT club_id, males, females, males/females AS ratio
  FROM school_clubs;

You can use the function NULLIF to avoid division by zero. NULLIF compares two expressions and returns null if they are equal or the first expression otherwise.

Rewrite the query as:

SELECT club_id, males, females, males/NULLIF(females, 0) AS ratio
  FROM school_clubs;

Any number divided by NULL gives NULL, and no error is generated.