例如：
id?????????? name???????? value
1?????????????? a???????????????? pp
2?????????????? a???????????????? pp
3?????????????? b???????????????? iii
4?????????????? b???????????????? pp
5?????????????? b???????????????? pp
6?????????????? c???????????????? pp
7?????????????? c???????????????? pp
8?????????????? c???????????????? iii
id是主鍵
要求得到這樣的結果
id?????????? name???????? value
1?????????????? a???????????????? pp
3?????????????? b???????????????? iii
4?????????????? b???????????????? pp
6?????????????? c???????????????? pp
8?????????????? c???????????????? iii
方法1
delete?? YourTable??
where?? [id]?? not?? in?? (
select?? max([id])?? from?? YourTable??
group?? by?? (name?? +?? value))
方法2
delete?? a
from?? 表?? a?? left?? join(
select?? id=min(id)?? from?? 表?? group?? by?? name,value
)b?? on?? a.id=b.id
where?? b.id?? is?? null
查詢及刪除重復記錄的SQL語句
查詢及刪除重復記錄的SQL語句
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)
(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，
現在就是需要查詢出在該表中的各記錄之間，“name”值存在重復的項；
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
＂重復記錄＂有兩個意義上的重復記錄，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，增加唯一索引列即可解決。
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)
最后一個select即得到了Name，Address不重復的結果集（但多了一個autoID字段，實際寫時可以寫在select子句中省去此列）
(四)
查詢重復
select * from tablename where id in (
select id from tablename
group by id
having count(id) > 1
)
轉自 http://www.cnblogs.com/sunxiaonan/archive/2009/11/24/1609439.html
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