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(jié)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(fù)記錄的SQL語句
查詢及刪除重復(fù)記錄的SQL語句
1挑豌、查找表中多余的重復(fù)記錄唆垃，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)記錄杨伙，重復(fù)記錄是根據(jù)單個字段（peopleId）來判斷爽航，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蚓让、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）讥珍，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历极、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”衷佃，
而且不同記錄之間的“name”值有可能會相同趟卸，
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)的項氏义；
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() >锄列； 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(fù)記錄＂有兩個意義上的重復(fù)記錄，一是完全重復(fù)的記錄惯悠，也即所有字段均重復(fù)的記錄邻邮，二是部分關(guān)鍵字段重復(fù)的記錄，比如Name字段重復(fù)克婶，而其他字段不一定重復(fù)或都重復(fù)可以忽略筒严。
1、對于第一種重復(fù)情萤，比較容易解決鸭蛙，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）筋岛，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)生的规惰，增加唯一索引列即可解決。
2泉蝌、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揩晴，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勋陪，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
)
