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MySql数据查重、去重的实现

作者 : zfajax舫
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发布时间 : 6年前
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评论数 : 0
查看数 : 47

一、单字段（nick_name）

1、查出所有有重复记录的所有记录

select * from user where nick_name in
    (select nick_name from user group by nick_name having count(nick_name)>1);

2、查出有重复记录的各个记录组中id最大的记录

select * from user where id in (select max(id) from user group by nick_name having count(nick_name)>1);

3、查出多余的记录，不查出id最小的记录

select * from user where nick_name in
    (select nick_name from user group by nick_name having count(nick_name)>1)
and id not in
    (select min(id) from user group by nick_name having count(nick_name)>1);

4、删除多余的重复记录，只保留id最小的记录

delete from user where nick_name in
    (select nick_name from
        (select nick_name from user group by nick_name having count(nick_name)>1) as tmp1)
and id not in
    (select id from
        (select min(id) from user group by nick_name having count(nick_name)>1) as tmp2);

二、多字段（nick_name,password）

1、查出所有有重复记录的记录

select * from user where (nick_name,password) in
    (select nick_name,password from user group by nick_name,password where having count(nick_name)>1);

2、查出有重复记录的各个记录组中id最大的记录

select * from user where id in
    (select max(id) from user group by nick_name,password where having count(nick_name)>1);

3、查出各个重复记录组中多余的记录数据，不查出id最小的一条

select * from user where (nick_name,password) in
    (select nick_name,password from user group by nick_name,password having count(nick_name)>1)
and id not in
    (select min(id) from user group by nick_name,password having count(nick_name)>1);

4、删除多余的重复记录，只保留id最小的记录

delete from user where (nick_name,password) in
    (select nick_name,password from
        (select nick_name,password from user group by nick_name,password having count(nick_name)>1) as tmp1)
and id not in
    (select id from
        (select min(id) id from user group by nick_name,password having count(nick_name)>1) as tmp2);