Logical NOT.
Return 1 if the operand is 0.
Return 0 if the operand is non-zero.
mysql> mysql> SELECT NOT 10; +--------+ | NOT 10 | +--------+ | 0 | +--------+ 1 row in set (0.00 sec) mysql> SELECT NOT 0; +-------+ | NOT 0 | +-------+ | 1 | +-------+ 1 row in set (0.00 sec)