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。
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select a.id,a.subject,a.RECEIVER from test1 a left join (select c.subject,c.RECEIVER ,max(c.id) asbid 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 anda.RECEIVER = b.RECEIVER anda.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。
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deletea from test1 a, (select c.subject,c.RECEIVER ,max(c.id) asbid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b where a.subject=b.subject anda.RECEIVER = b.RECEIVER anda.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
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select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
