Retrieving and excluding rows with null values

A null value indicates the absence of a column value in a row. A null value is not the same as zero or all blanks. You can retrieve or exclude rows that contain a null value in a specific row.

Begin general-use programming interface information.
Example 1: You can use a WHERE clause to retrieve rows that contain a null value in a specific column. Specify: 
WHERE column-name IS NULL
Example 2: You can also use a predicate to exclude null values. Specify: 
WHERE column-name IS NOT NULL
End general-use programming interface information.

You cannot use the equal sign to retrieve rows that contain a null value. (WHERE column-name = NULL is not allowed.)