mysql数据库怎样去掉反复数据

mysql数据库去除反复数据的办法：1、查询需要删除的记载，会保存一笔记录；2、删除反复记载，只保存一笔记录，代码为【delete a from test1 a, (...)as bid from test1 c where..】。

mysql数据库去除反复数据的办法：

1、查询需要删除的记载，会保存一笔记录。

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、删除反复记载，只保存一笔记录。留意，subject,RECEIVER 要索引，不然会很慢的。

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、查寻表中余外的反复记载，反复记载是按照单个字段（peopleId）来推断

select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

4、删除表中余外的反复记载，反复记载是按照单个字段（peopleId）来推断，只留有rowid最小的记载

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、删除表中余外的反复记载（多个字段），只留有rowid最小的记载

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仿佛不太显示，还是老诚实实的分步处置吧，思绪先创立复制一个暂时表，然后对照暂时表内的数据，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;