CREATE TABLE `t1` (
`user_id` int DEFAULT NULL,
`name` varchar(10) DEFAULT NULL,
`address` varchar(10) DEFAULT NULL,
KEY `idx_userid` (`user_id`)
) ENGINE=InnoDB
mysql> select * from t1;
+---------+------+---------+
| user_id | name | address |
+---------+------+---------+
| 10 | aa | bj |
| 20 | bb | sh |
| 30 | cc | NULL |
+---------+------+---------+
3 rows in set (0.00 sec)
查询不等于台湾的数据
mysql> select * from t1 where address != 'taiwan';
+---------+------+---------+
| user_id | name | address |
+---------+------+---------+
| 10 | aa | bj |
| 20 | bb | sh |
+---------+------+---------+
2 rows in set (0.06 sec)
mysql> select * from t1 where address <> 'taiwan';
+---------+------+---------+
| user_id | name | address |
+---------+------+---------+
| 10 | aa | bj |
| 20 | bb | sh |
+---------+------+---------+
2 rows in set (0.00 sec)
按照人类的思维应该返回3条数据,但却返回了2条数据。
原创声明:本文系作者授权腾讯云开发者社区发表,未经许可,不得转载。
如有侵权,请联系 cloudcommunity@tencent.com 删除。
原创声明:本文系作者授权腾讯云开发者社区发表,未经许可,不得转载。
如有侵权,请联系 cloudcommunity@tencent.com 删除。