SQL重复记录查询(转载)

布满荆棘的人生 2022-06-10 11:46 234阅读 0赞

**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  
![None.gif][]select\*from  people  
![None.gif][]where peopleId in (select peopleId from people groupby peopleId havingcount(peopleId) >**1** )

例二：

select \* from testtable

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

可以查出testtable表中number相同的记录  
![None.gif][]  
![None.gif][]**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  
![None.gif][]deletefrom  people  
![None.gif][]where peopleId in (select peopleId from people groupby peopleId havingcount(peopleId) >**1** )  
![None.gif][]and rowid notin (selectmin(rowid) from people groupby peopleId havingcount(peopleId )>**1** )  
![None.gif][]  
![None.gif][]**3** 、查找表中多余的重复记录（多个字段）  
![None.gif][]select\*from  vitae a  
![None.gif][]where (a.peopleId,a.seq) in (select peopleId,seq from vitae groupby peopleId,seq havingcount(\*) >**1** )  
![None.gif][]  
![None.gif][]**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  
![None.gif][]deletefrom  vitae a  
![None.gif][]where (a.peopleId,a.seq) in (select peopleId,seq from vitae groupby peopleId,seq havingcount(\*) >**1** )  
![None.gif][]and rowid notin (selectmin(rowid) from vitae groupby peopleId,seq havingcount(\*)>**1** )  
![None.gif][]  
![None.gif][]  
![None.gif][]**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  
![None.gif][]select\*from  vitae a  
![None.gif][]where (a.peopleId,a.seq) in (select peopleId,seq from vitae groupby peopleId,seq havingcount(\*) >**1** )  
![None.gif][]and rowid notin (selectmin(rowid) from vitae groupby peopleId,seq havingcount(\*)>**1** )  
![None.gif][]  
![None.gif][](二)  
![None.gif][]比方说  
![None.gif][]在A表中存在一个字段“name”，  
![None.gif][]而且不同记录之间的“name”值有可能会相同，  
![None.gif][]现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；  
![None.gif][]Select Name,Count(\*) From A GroupBy Name HavingCount(\*) >**1**   
![None.gif][]  
![None.gif][]如果还查性别也相同大则如下:  
![None.gif][] Select Name,sex,Count(\*) From A GroupBy Name,sex HavingCount(\*) >**1**   
![None.gif][]  
![None.gif][]  
![None.gif][](三)  
![None.gif][]方法一  
![None.gif][]  
![None.gif][] declare@max**integer**,@id**integer**   
![None.gif][]  
![None.gif][] declare cur\_rows cursor local forselect 主字段,count(\*) from 表名 groupby 主字段 havingcount(\*) >； **1**   
![None.gif][]  
![None.gif][] open  cur\_rows  
![None.gif][]  
![None.gif][]fetch cur\_rows into@id,@max   
![None.gif][]  
![None.gif][] while**@@fetch\_status**=**0**   
![None.gif][]  
![None.gif][] begin   
![None.gif][]  
![None.gif][] select@max=@max\-**1**   
![None.gif][]  
![None.gif][] setrowcount@max   
![None.gif][]  
![None.gif][] deletefrom 表名 where 主字段 =@id   
![None.gif][]  
![None.gif][] fetch cur\_rows into@id,@max   
![None.gif][]  
![None.gif][] end   
![None.gif][]  
![None.gif][] close  cur\_rows  
![None.gif][]  
![None.gif][]setrowcount**0**   
![None.gif][]  
![None.gif][]方法二  
![None.gif][]  
![None.gif][]　　有两个意义上的重复记录，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。  
![None.gif][]  
![None.gif][] **1** 、对于第一种重复，比较容易解决，使用  
![None.gif][]  
![None.gif][]selectdistinct\*from  tableName  
![None.gif][]  
![None.gif][]就可以得到无重复记录的结果集。  
![None.gif][]  
![None.gif][]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  
![None.gif][]  
![None.gif][]selectdistinct\*into \#Tmp from  tableName  
![None.gif][]  
![None.gif][]droptable  tableName  
![None.gif][]  
![None.gif][]select\*into tableName from  \#Tmp  
![None.gif][]  
![None.gif][]droptable  \#Tmp  
![None.gif][]  
![None.gif][]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。  
![None.gif][]  
![None.gif][]**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  
![None.gif][]  
![None.gif][]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  
![None.gif][]  
![None.gif][]selectidentity(**int**,**1**,**1**) as autoID, \*into \#Tmp from  tableName  
![None.gif][]  
![None.gif][]selectmin(autoID) as autoID into \#Tmp2 from \#Tmp groupby  Name,autoID  
![None.gif][]  
![None.gif][]select\*from \#Tmp where autoID in(select autoID from  \#tmp2)  
![None.gif][]  
![None.gif][]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）  
![None.gif][]  
![None.gif][](四)

![None.gif][]查询重复  
![None.gif][]  
![None.gif][]select\*from tablename where id in  (  
![None.gif][]  
![None.gif][]select id from  tablename  
![None.gif][]  
![None.gif][]groupby  id  
![None.gif][]  
![None.gif][]havingcount(id) >**1**   
![None.gif][]  
![None.gif][])

[None.gif]: /images/20220610/33e68a472ba64f458a0f08adceb99260.png