mysql 刪除表中的某列的重復字段

假設：

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,'小張','男'),
(null,'小趙','女'),
(null,'tom','男'),
(null,'jack','男'),
(null,'小趙','女');

 

 

刪除重復字段SQL代碼

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;

 

詳細解釋

1、首先把所有重復的第一個字段取出

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

2、再與原表組成對照表

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

3、取出重復第一個字段的id號以外的所有字段

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、進行刪除

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;