Logical operators
Table 1. Logical operators
Operator |
Description |
Example |
AND |
The result is TRUE if both values are TRUE. |
a AND b |
OR |
The result is TRUE if either value is TRUE. |
a OR b |
NOT |
The result is TRUE if the value is FALSE. |
NOT a |
Effect of NULL on logical operators
The following tables list the truth values when the values of a and b are TRUE, FALSE,
and NULL, respectively.
Table 2. Truth table 1
a |
b |
a AND b |
a OR b |
TRUE |
TRUE |
TRUE |
TRUE |
TRUE |
FALSE |
FALSE |
TRUE |
TRUE |
NULL |
NULL |
TRUE |
FALSE |
TRUE |
FALSE |
TRUE |
FALSE |
FALSE |
FALSE |
FALSE |
FALSE |
NULL |
FALSE |
NULL |
NULL |
TRUE |
NULL |
TRUE |
NULL |
FALSE |
FALSE |
NULL |
NULL |
NULL |
NULL |
NULL |
Table 3. Truth table 2
a |
NOT a |
TRUE |
FALSE |
FALSE |
TRUE |
NULL |
NULL |