Recipe1.11.Finding Null Values

Recipe 1.11. Finding Null Values

Problem

You want to find all rows that are null for a particular column.

Solution

To determine whether a value is null, you must use IS NULL:

 1 select * 2   from emp 3  where comm is null 

Discussion

NULL is never equal/not equal to anything, not even itself, therefore you cannot use = or != for testing whether a column is NULL. To determine whether or not a row has NULL values you must use IS NULL. You can also use IS NOT NULL to find rows without a null in a given column.