If either operand of a comparison operator is null, then the result is unknown and an error is returned to the requestor. The following examples indicate this behavior.
| Expression | Result | Error Message |
|---|---|---|
| 5 = NULL | Unknown | 3731 |
| 5 <> NULL | ||
| NULL = NULL | ||
| NULL <> NULL | ||
| 5 = NULL + 5 |
If the argument of the NOT operator is unknown, the result is also unknown. This evaluation translates to FALSE as a final boolean result.