mysql 去除重复记录
有如下sql
SET FOREIGN_KEY_CHECKS=0;
DROP TABLE IF EXISTS `count`;
CREATE TABLE `count` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`a1` int(11) NOT NULL,
`b1` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=latin1;
INSERT INTO `count` VALUES ('1', '1', '1');
INSERT INTO `count` VALUES ('2', '7', '2');
INSERT INTO `count` VALUES ('3', '2', '1');
INSERT INTO `count` VALUES ('4', '6', '2');
INSERT INTO `count` VALUES ('5', '5', '3');
INSERT INTO `count` VALUES ('6', '2', '0');
INSERT INTO `count` VALUES ('7', '2', '4');

希望获取a1字段值和b1字段值都不重复的记录

返回的正确结果应该是

id a1 b1
'5' '5' '3'

[解决办法]

SQL code

mysql> select * from `count`;+----+----+----+| id | a1 | b1 |+----+----+----+|  1 |  1 |  1 ||  2 |  7 |  2 ||  3 |  2 |  1 ||  4 |  6 |  2 ||  5 |  5 |  3 ||  6 |  2 |  0 ||  7 |  2 |  4 |+----+----+----+7 rows in set (0.00 sec)mysql> select * from `count` t    -> where not exists (select 1 from `count` where (a1=t.a1 or b1=t.b1) and id!=t.id);+----+----+----+| id | a1 | b1 |+----+----+----+|  5 |  5 |  3 |+----+----+----+1 row in set (0.00 sec)mysql>