mysql中如何去除重复数据_mysql数据库如何去除重复数据

mysql数据库去除重复数据的方法：1、查询需要删除的记录，会保留一条记录；2、删除重复记录，只保留一条记录，代码为【delete a from test1 a, (...)as bid from test1 c where..】。

mysql数据库去除重复数据的方法：

1、查询需要删除的记录，会保留一条记录。select a.id,a.subject,a.RECEIVER from test1 a left join (select c.subject,c.RECEIVER ,max(c.id) as bid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b on a.id< b.bid where a.subject=b.subject and a.RECEIVER = b.RECEIVER and a.id < b.bid

2、删除重复记录，只保留一条记录。注意，subject,RECEIVER 要索引，否则会很慢的。delete a from test1 a, (select c.subject,c.RECEIVER ,max(c.id) as bid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b where a.subject=b.subject and a.RECEIVER = b.RECEIVER and a.id < b.bid;

3、查找表中多余的重复记录，重复记录是根据单个字段(peopleId)来判断select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

4、删除表中多余的重复记录，重复记录是根据单个字段(peopleId)来判断，只留有rowid最小的记录delete from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1) and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>1)

5、删除表中多余的重复记录(多个字段)，只留有rowid最小的记录delete from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

看来想偷懒使用一句命令完成这个事好像不太显示，还是老老实实的分步处理吧，思路先建立复制一个临时表，然后对比临时表内的数据，删除主表里的数据alter table tableName add autoID int auto_increment not null;

create table tmp select min(autoID) as autoID from tableName group by Name,Address;

create table tmp2 select tableName.* from tableName,tmp where tableName.autoID = tmp.autoID;

drop table tableName;

rename table tmp2 to tableName;更多相关免费学习推荐：mysql教程(视频)

如果觉得《mysql中如何去除重复数据_mysql数据库如何去除重复数据》对你有帮助，请点赞、收藏，并留下你的观点哦！