SQL查询重复记录方法大全

2019-09-04 16:39:41 浏览数 (1)

查找所有重复标题的记录:

SELECT * FROM t_info a WHERE ((SELECT COUNT(*) FROM t_info WHERE Title = a.Title) > 1) ORDER BY Title DESC

一。查找重复记录

1。查找全部重复记录

Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2。过滤重复记录(只显示一条)

Select * From HZT Where ID In (Select Max(ID) From HZT Group By Title)

注:此处显示ID最大一条记录

二。删除重复记录

1。删除全部重复记录(慎用)

Delete FROM 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2。保留一条(这个应该是大多数人所需要的 ^_^)

Delete FROM HZT Where ID Not In (Select Max(ID) From HZT Group By Title)

注:此处保留ID最大一条记录

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 people where 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 a where (a.peopleId,a.seq) in   (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) 4、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) 5、查找表中多余的重复记录(多个字段),不包含rowid最小的记录 select * 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)

补充:

有两个以上的重复记录,一是完全重复的记录,也即所有字段均重复的记录,二是部分关键字段重复的记录,比如Name字段重复,而其他字段不一定重复或都重复可以忽略。 1、对于第一种重复,比较容易解决,使用 select distinct * from tableName 就可以得到无重复记录的结果集。 如果该表需要删除重复的记录(重复记录保留1条),可以按以下方法删除 select distinct * into #Tmp from tableName drop table tableName select * into tableName from #Tmp drop table #Tmp 发生这种重复的原因是表设计不周产生的,增加唯一索引列即可解决。 2、这类重复问题通常要求保留重复记录中的第一条记录,操作方法如下 假设有重复的字段为Name,Address,要求得到这两个字段唯一的结果集 select identity(int,1,1) as autoID, * into #Tmp from tableName select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID select * from #Tmp where autoID in(select autoID from #tmp2) 最后一个select即得到了Name,Address不重复的结果集(但多了一个autoID字段,实际写时可以写在select子句中省去此列)

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