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
三、舉例
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)
四、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、對于第一種重復,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,增加唯一刪除列即可解決。
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)
? 版權聲明
文章版權歸作者所有,未經允許請勿轉載。
THE END