NOT,!
运算符说明
NOT,!
逻辑运算符用作于逻辑非运算。如果操作数为零,则返回结果为 true
;如果操作数非零,则返回结果为 false
;如果操作数为 NOT NUL
则返回 NULL
。
语法结构
> NOT|! value
示例
mysql> select not 0;
+-------+
| not 0 |
+-------+
| true |
+-------+
1 row in set (0.02 sec)
mysql> select ! null;
+-------+
| !null |
+-------+
| NULL |
+-------+
1 row in set (0.00 sec)
mysql> select ! 1;
+-------+
| !1 |
+-------+
| false |
+-------+
1 row in set (0.01 sec)
create table t1 (a boolean,b bool);
insert into t1 values (0,1),(true,false),(true,1),(0,false),(NULL,NULL);
mysql> SELECT * FROM T1;
+-------+-------+
| a | b |
+-------+-------+
| false | true |
| true | false |
| true | true |
| false | false |
| NULL | NULL |
+-------+-------+
5 rows in set (0.01 sec)
mysql> select not a and not b from t1;
+-----------------+
| not a and not b |
+-----------------+
| false |
| false |
| false |
| true |
| NULL |
+-----------------+
5 rows in set (0.00 sec)
mysql> select * from t1 where !(a=false);
+------+-------+
| a | b |
+------+-------+
| true | false |
| true | true |
+------+-------+
2 rows in set (0.00 sec)