轉載請註明出處:http://blog.csdn.net/l1028386804/article/details/51733585
查找所有重複標題的記錄:
- SELECT * FROM t_info a WHERE ((SELECT COUNT(*) FROM t_info WHERE Title = a.Title) > 1) ORDER BY Title DESC
SELECT * FROM t_info a WHERE ((SELECT COUNT(*) FROM t_info WHERE Title = a.Title) > 1) ORDER BY Title DESC
一、查找重複記錄
1、查找全部重複記錄
- Select * From 表 Where 重複字段 In (Select 重複字段 From 表 Group By 重複字段 Having Count(*)>1)
Select * From 表 Where 重複字段 In (Select 重複字段 From 表 Group By 重複字段 Having Count(*)>1)
2、過濾重複記錄(只顯示一條)
- Select * From HZT Where ID In (Select Max(ID) From HZT Group By Title)
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、刪除重複記錄
1、刪除全部重複記錄(慎用)
- Delete 表 Where 重複字段 In (Select 重複字段 From 表 Group By 重複字段 Having Count(*)>1)
Delete 表 Where 重複字段 In (Select 重複字段 From 表 Group By 重複字段 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)
Delete HZT Where ID Not In (Select Max(ID) From HZT Group By Title)
注:此處保留ID最大一條記錄三、舉例
1、查找表中多餘的重複記錄,重複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)
select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
2、刪除表中多餘的重複記錄,重複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)
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、查找表中多餘的重複記錄(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)
select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
4、刪除表中多餘的重複記錄(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)
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、查找表中多餘的重複記錄(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)
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)
四、補充
有兩個以上的重複記錄,一是完全重複的記錄,也即所有字段均重複的記錄,二是部分關鍵字段重複的記錄,比如Name字段重複,而其他字段不一定重複或都重複可以忽略。
1、對於第一種重複,比較容易解決,使用
- select distinct * from tableName
select distinct * from tableName
就可以得到無重複記錄的結果集。如果該表需要刪除重複的記錄(重複記錄保留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
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
發生這種重複的原因是表設計不周產生的,增加唯一索引列即可解決。2、這類重複問題通常要求保留重複記錄中的第一條記錄,操作方法如下
假設有重複的字段爲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)
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)