Logical Operators¶
Common logical operators include AND, OR, and NOT. The operation result can be TRUE, FALSE, or NULL (which means unknown). The priorities of the operators are as follows: NOT > AND > OR.
Table 1 lists the calculation rules, where A and B represent logical expressions.
Operator | Result Type | Description |
|---|---|---|
A AND B | BOOLEAN | If A and B are TRUE, then TRUE is returned. Otherwise, FALSE is returned. If A or B is NULL, then NULL is returned. |
A OR B | BOOLEAN | If A or B is TRUE, then TRUE is returned. Otherwise, FALSE is returned. If A or B is NULL, then NULL is returned. If one is TRUE and the other is NULL, then TRUE is returned. |
NOT A | BOOLEAN | If A is FALSE, then TRUE is returned. If A is NULL, then NULL is returned. Otherwise, FALSE is returned. |
! A | BOOLEAN | Same as NOT A. |
A IN (val1, val2, ...) | BOOLEAN | If A is equal to any value in (val1, val2, ...), then TRUE is returned. Otherwise, FALSE is returned. |
A NOT IN (val1, val2, ...) | BOOLEAN | If A is not equal to any value in (val1, val2, ...), then TRUE is returned. Otherwise, FALSE is returned. |
EXISTS (subquery) | BOOLEAN | If the result of any subquery contains at least one line, then TRUE is returned. Otherwise, FALSE is returned. |
NOT EXISTS (subquery) | BOOLEAN | If the subquery output does not contain any row, TRUE is returned; otherwise, FALSE is returned. |