Comparing nullable columns

Do you ever compare the values of a lot of columns in two tables? Sure you do. Like, for instance, in a cross update, when you need to figure out which rows you should actually update. But it gets worse if the columns are nullable. The fact that any value could potentially be NULL vastly complicates the comparison and might wreak havoc not only on your code but also on your query performance.

But there’s hope.

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Using NULLIF() to avoid division by zero

When you perform divisions, you need to make sure that the divisor, the number to the right of the division operator, isn’t zero. If it is, you will end up with a division-by-zero error message:

Msg 8134, Level 16, State 1, Line 1
Divide by zero error encountered.

Dividing by NULL, however, doesn’t. So to avoid division-by-zero errors, simply use NULLIF() to replace zeros in the divisor with a NULL value.

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