SQL重（chóng）複記錄查詢(轉載)
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)

例二：
select * from testtable
where numeber in (select number from people group by number having count(number) > 1 )
可以（yǐ）查出testtable表中number相（xiàng）同的記錄

2、刪除表中多餘的重複記錄，重複記錄是（shì）根據單個（gè）字段（peopleId）來判斷，隻留有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（duō）餘（yú）的重複記（jì）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（chóng）複記錄（多個字段），隻留（liú）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（duàn）），不（bú）包含rowid最（zuì）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（zài）一個字段（duàn）“name”，
而且不同記錄之間的“name”值有可能會相同，
現在就是需（xū）要查詢出（chū）在該表中的各記錄之間，“name”值存在重複的項；
Select Name,Count(*) From A Group By Name Having Count(*) > 1

如（rú）果還查性別也相（xiàng）同（tóng）大（dà）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（shàng）的重複記錄，一是完全重複的記錄，也（yě）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（duàn）重複，而其他字段不一（yī）定重（chóng）複或都重複可以忽（hū）略（luè）。

1、對於第一種重複，比較容易解決，使用

select distinct * from tableName

就可以得（dé）到無重複記錄的結果集。

如果該（gāi）表需（xū）要刪除（chú）重複的（de）記（jì）錄（重複記錄保留1條），可（kě）以按以下（xià）方法刪（shān）除

select distinct * into #Tmp from tableName

drop table tableName

select * into tableName from #Tmp

drop table #Tmp

發生這種重（chóng）複的原（yuán）因是表設計不周產生的，增加唯一索（suǒ）引列即可解決。

2、這類重（chóng）複問題通常要求保留重複記錄中的第一條記錄（lù），操作方法如（rú）下

假（jiǎ）設有重複的字（zì）段為Name,Address，要求得到這兩個字段唯（wéi）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（zuì）後一個select即得（dé）到了Name，Address不重複的結（jié）果集（但多了一個autoID字段，實際寫時（shí）可（kě）以寫在select子句中省去此（cǐ）列）

(四)

查詢重複

select * from tablename where id in (

select id from tablename

group by id

having count(id) > 1

)