The following tables display how the AND, OR, NOT, and IS logical operators of SQL work in three-valued logic.
AND operator| AND | TRUE | FALSE | UNKNOWN |
|---|---|---|---|
| TRUE | TRUE | FALSE | UNKNOWN |
| FALSE | FALSE | FALSE | FALSE |
| UNKNOWN | UNKNOWN | FALSE | UNKNOWN |
OR operator| OR | TRUE | FALSE | UNKNOWN |
|---|---|---|---|
| TRUE | TRUE | TRUE | TRUE |
| FALSE | TRUE | FALSE | UNKNOWN |
| UNKNOWN | TRUE | UNKNOWN | UNKNOWN |
NOT operator| TRUE | FALSE | UNKNOWN |
|---|---|---|
| FALSE | TRUE | UNKNOWN |
IS operator| IS | TRUE | FALSE | UNKNOWN |
|---|---|---|---|
| TRUE | TRUE | FALSE | FALSE |
| FALSE | FALSE | TRUE | FALSE |
| UNKNOWN | FALSE | FALSE | TRUE |
Standards and compatibilitySQL/2008 Core feature. Truth value tests, such as IS UNKNOWN, comprise SQL language feature F571.
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