数据库去重复查询 怎样查询数据库中重复的数据?
怎样查询数据库中重复的数据?
1、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 peoplewhere peopleId in (select peopleId from people group by peopleId having count (peopleId) > 1)
2、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)
3、查找表中多余的重复记录(多个字段)
select * from vitae awhere (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having
SQL数据库多表连接查询为什么数据会重复?
1、用select语句,查看两个表中的数据,确认下来的结果是每个表中都只有两行数据;
2、尝试着用最常用的两表结合查询方式来看看结果----结果重复出现,并且结果错误:select a.pono,a.p_name,a.p_kg as 系统重量,b.p_kg as 实际重量 from test1 a,test2 b where a.pono=b.sono;
3、执行完整代码,可以得出结果,select isnull(a.pono,b.sono) as pono,isnull(a.p_name,b.p_name) as p_name, a.p_kg as 系统重量、 b.p_kg as 实际重量、 from test1 as a 、full join test2 as b on a.pono = b.sono、and a.p_name = b.p_name。
数据库去重复查询 mysql删除表中重复数据 sql删除表中重复数据
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