SQL的重複記錄處理大全

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 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) 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) 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 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。保留一條（這個應該是大多數人所需要的 ^_^） Delete FROM 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) 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) 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) 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) 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) 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 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 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) 最後一個select即得到了Name，Address不重複的結果集（但多了一個autoID字段，實際寫時可以寫在select子句中省去此列）