MySQL删除重复数据行，只保留一条

花花世界蕾

　　
　　

delimiter $$
CREATE TABLE `devices_all` (
`device_all_id` int(11) NOT NULL AUTO_INCREMENT,
`device_id` varchar(512) DEFAULT NULL,
`device_token` varchar(512) DEFAULT NULL,
`client_agent` varchar(512) DEFAULT NULL,
`create_time` datetime DEFAULT NULL,
PRIMARY KEY (`device_all_id`)
) ENGINE=MyISAM AUTO_INCREMENT=49 DEFAULT CHARSET=latin1$$

　　
　　表名devices_all,判重列[size=1em]device_id。 
　　

delete from devices_all
where device_id in (select  device_id from  (select device_id from  devices_all  a  group by a.device_id having count(a.device_id) > 1) as a)
and device_all_id not in (select device_all_id from (select min( device_all_id) device_all_id from devices_all group by  device_id having count( device_id)>1) as b)