sql語句查詢重復的數據

查找所有重復標題的記錄：

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

一。查找重復記錄

1。查找全部重復記錄

Select * From 表 Where 重復字段 In (Select 重復字段 From 表 Group By 重復字段 Having Count(*)>1)

2。過濾重復記錄(只顯示一條)

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

注：此處顯示ID最大一條記錄

二。刪除重復記錄


1。刪除全部重復記錄（慎用）

Delete 表 Where 重復字段 In (Select 重復字段 From 表 Group By 重復字段 Having Count(*)>1)

2。保留一條（這個應該是大多數人所需要的 ^_^）

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

注：此處保留ID最大一條記錄

1、查找表中多余的重復記錄，重復記錄是根據單個字段（peopleId）來判斷

select * from people

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



2、刪除表中多余的重復記錄，重復記錄是根據單個字段（peopleId）來判斷，只留有rowid最小的記錄

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、查找表中多余的重復記錄（多個字段）

select * from vitae a

where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)



4、刪除表中多余的重復記錄（多個字段），只留有rowid最小的記錄

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、查找表中多余的重復記錄（多個字段），不包含rowid最小的記錄

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)


補充：

有兩個以上的重復記錄，一是完全重復的記錄，也即所有字段均重復的記錄，二是部分關鍵字段重復的記錄，比如Name字段重復，而其他字段不一定重復或都重復可以忽略。


1、對於第一種重復，比較容易解決，使用

select distinct * from tableName


就可以得到無重復記錄的結果集。



如果該表需要刪除重復的記錄（重復記錄保留1條），可以按以下方法刪除

select distinct * into #Tmp from tableName

drop table tableName

select * into tableName from #Tmp

drop table #Tmp



發生這種重復的原因是表設計不周產生的，增加唯一索引列即可解決。


2、這類重復問題通常要求保留重復記錄中的第一條記錄，操作方法如下

假設有重復的字段為Name,Address，要求得到這兩個字段唯一的結果集

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)