文章轉(zhuǎn)載自：http://www.jb51.net/article/34820.html
SQL重復(fù)記錄查詢的幾種方法
1、查找表中多余的重復(fù)記錄，重復(fù)記錄是根據(jù)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(fù)記錄，重復(fù)記錄是根據(jù)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(fù)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(fù)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(fù)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)
```
(二)
比方說
在A表中存在一個字段“name”，
而且不同記錄之間的“name”值有可能會相同，
現(xiàn)在就是需要查詢出在該表中的各記錄之間，“name”值存在重復(fù)的項；
```
Select Name,Count(*) From A Group By Name Having Count(*) > 1
```
如果還查性別也相同大則如下:
```
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1
```
(三)
方法一
```
declare @max integer,@id integer
declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having
count(*) >； 1
open cur_rows
fetch cur_rows into @id,@max
while @@fetch_status=0
begin
select @max = @max -1
set rowcount @max
delete from 表名 where 主字段 = @id
fetch cur_rows into @id,@max
end
close cur_rows
set rowcount 0
```
方法二
有兩個意義上的重復(fù)記錄，一是完全重復(fù)的記錄，也即所有字段均重復(fù)的記錄，二是部分關(guān)鍵字段重
復(fù)的記錄，比如Name字段重復(fù)，而其他字段不一定重復(fù)或都重復(fù)可以忽略。
1、對于第一種重復(fù)，比較容易解決，使用
```
select distinct * from tableName
```
就可以得到無重復(fù)記錄的結(jié)果集。
如果該表需要刪除重復(fù)的記錄（重復(fù)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(fā)生這種重復(fù)的原因是表設(shè)計不周產(chǎn)生的，增加唯一索引列即可解決。
2、這類重復(fù)問題通常要求保留重復(fù)記錄中的第一條記錄，操作方法如下
假設(shè)有重復(fù)的字段為Name,Address，要求得到這兩個字段唯一的結(jié)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)
```
最后一個select即得到了Name，Address不重復(fù)的結(jié)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）
(四)查詢重復(fù)
```
select * from tablename where id in ( select id from tablename group by id
having count(id) > 1)
```
