NULL operators

To check whether a value is or is not NULL, use the following equivalent constructs:.

To check whether a value is or is not NULL, use the following equivalent constructs:

Standard:

[expression IS NULL | expression IS NOT NULL]

Non-standard:

[expression ISNULL | expression NOTNULL]

Do not write expression = NULL: NULL represents an unknown value, and two unknown values are not necessarily equal. This behavior conforms to the SQL standard.

Note

Some applications might expect that expression = NULL returns true if expression evaluates to NULL. In this case, modify the application to comply with the SQL standard.