mysql 删除表中的某列的重复字段

假设：

create table t(
id int not null primary key auto_increment,
name char(10) not null,
sex char(2) not null
)engine=myisam;

insert into t values
(null,‘tom‘,‘男‘),
(null,‘jack‘,‘男‘),
(null,‘小文‘,‘男‘),
(null,‘小文‘,‘女‘),
(null,‘tom‘,‘男‘),
(null,‘小张‘,‘男‘),
(null,‘小赵‘,‘女‘),
(null,‘tom‘,‘男‘),
(null,‘jack‘,‘男‘),
(null,‘小赵‘,‘女‘);

删除重复字段SQL代码

delete t as a
from t as a,
(select * from t group by name having count(1)>1) as b
where a.name=b.name
and a.id > b.id;

详细解释

1、首先把所有重复的第一个字段取出

select * from t group by name having count(1)>1

2、再与原表组成对照表

select * from t as a,
(select * from t group by name having count(1)>1) as b
where a.name=b.name;

3、取出重复第一个字段的id号以外的所有字段

select * from t as a,
(select * from t group by name having count(1)>1) as b
where a.name=b.name
and a.id > b.id;

4、进行删除

delete t as a
from t as a,
(select * from t group by name having count(1)>1) as b
where a.name=b.name
and a.id > b.id;