mysql 查询及 删除表中重复数据

CREATE TABLE `test` (
	`id` INT(20) NOT NULL AUTO_INCREMENT,
	`name` VARCHAR(20) NULL DEFAULT NULL,
	`age` INT(5) NULL DEFAULT NULL,
	PRIMARY KEY (`id`)
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB

　　

查询出所有重复的记录 ，删除所有 select a.* 换成delete 

select a.* 
from test a 
join (select name,count(*) from test group by name having count(*)> 1 ) b 
on a.name = b.name;

　　

查询不重复的记录，和重复记录里最后插入的记录 

select * from test a where a.id = (select max(id) from test b where a.name = b.name);

　

查询不重复的记录。和重复记录里,最先插入的记录 

select * from test a where a.id = (select min(id) from test b where a.name = b.name);

　　

查询出重复记录里，第一条重复记录以外的所有重复记录 删除的话select * 换成delete

select * from test a where a.id != (select min(id) from test b where a.name = b.name);

　　

查询出重复记录里，最后一条重复记录以外所有重复的记录 ，删除的话select * 换成delete

select * from test a where a.id != (select max(id) from test b where a.name = b.name);