AND,&&
运算符说明
AND,&&
逻辑运算符用作于逻辑与运算。如果所有操作数都非零且不为 NULL
,则返回结果为 true
;如果一个或多个操作数为 0,则返回结果为 false
;如果一个或多个操作数非零且为 NULL
,则返回 NULL
。
语法结构
> SELECT column_1 AND column_2 FROM table_name;
示例
mysql> select 1 and 1;
+---------+
| 1 and 1 |
+---------+
| true |
+---------+
mysql> select 1 and 0;
+---------+
| 1 and 0 |
+---------+
| false |
+---------+
mysql> select 1 and null;
+------------+
| 1 and null |
+------------+
| NULL |
+------------+
mysql> select null and 0;
+------------+
| null and 0 |
+------------+
| 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 a and b from t1;
+---------+
| a and b |
+---------+
| false |
| false |
| true |
| false |
| NULL |
+---------+
5 rows in set (0.00 sec)