常用（经典）ＳＱＬ语句汇总贴
背景：最近想好好学习下ＳＱＬ语言，欢迎大家提供比较常用的或经典的ＳＱＬ语句！！谢谢！！
转自：青松Blog:http://www.cnblogs.com/piaoqingsong/archive/2006/08/08/470931.html
删除重复数据
1、delete from t1 where exists(select 1 from t1 a where a.id>t1.id and t1.col1=a.col1)
2、alter table t1 add (id int identity(1,1))
delete from t1
where id not in (select min(id) from t1 group by column having count(*) > 0)
3、 delete from music a1 where a1.rowid<>(select max(rowid) from music a2 where a1.id=a2.id )
考虑一下，第一条处理方案最好，方案3也不错，rowid是Oracle特有的，不过根据唯一标识在别的数据库也一样处理
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我这里有一些,希望你能有用.
--如何按字段删除重复记录
一张表里面以两个字段为唯一字段，当几条记录的这两个字段完全相同时，需要删除重复项，如下表
a b c d
1 2 3 4
1 5 3 5
1 2 7 9
以a、b为唯一字段，第一条和第三条的a、b完全相同，所以，需要删除第一条记录1 2 3 4 或者第三条记录1 2 7 9
即如下结果：
a b c d
1 2 3 4
1 5 3 5
或
a b c d
1 5 3 5
1 2 7 9
请问各位大侠这种sql语句怎么写
CREATE TABLE Tb1(id int, [a] varchar(255), [b] varchar(255), [c] varchar(255), [d] varchar(255))
INSERT Tb1(id, [a], [b], [c], [d])
SELECT 1, '1','2','3','4'
UNION ALL SELECT 2, '1','5','3','5'
UNION ALL SELECT 3, '1','2','7','9'
UNION ALL SELECT 4, '1','4','7','6'
delete Tb1 where [id] not in (select max([id]) from Tb1 group by a,b )
select * from tb1
drop table tb1
如果要同时删除第一和第三行
即如下结果：
a b c d
1 5 3 5
语句如下：
delete m from tb t
inner join
(
select a ,b
from tb
group by a , b
having count(*)>1
)n
on m.a = n.a and m.b = n.b
或
delete * from tb as m,
(
select a ,b
from tb
group by a , b
having count(*)>1
)n
where m.a = n.a and m.b = n.b
------------------------------------------------
在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢?谢谢!
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
select * from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
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
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、查找表中多余的重复记录（多个字段）
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
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、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
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)
比方说在A表中存在一个字段“name”，而且不同记录之间的“name”值有可能会相同，
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；
Select Name,Count(*) From A Group By Name Having Count(*) > 1
如果还查性别也相同大则如下:
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1
------------------------------------------------------------
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。
1、对于第一种重复，比较容易解决，使用
select distinct * from tableName
就可以得到无重复记录的结果集。
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
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
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。
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
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
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）
select * from tablename where id in (
select id from tablename
group by id
having count(id) > 1)
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先看看这几帖 :)
SQL 收藏--SQL操作全集
http://topic.csdn.net/u/20080515/16/6f359854-5403-4397-89e3-b1b8dd71d527.html
SQL语句优化汇总
http://topic.csdn.net/u/20080716/11/2317d040-48e7-42da-822e-040b4c55b46d.html
分享--整理了一些t-sql技巧
http://topic.csdn.net/u/20080605/15/ca6b25f3-3e60-4b95-ac7e-7d7dc02354e6.html
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不错，先收藏再说
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delete m from tb m -- t改成 m inner join ( select a ,b from tb group by a , b having count(*)>1 )n on m.a = n.a and m.b = n.b
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多表关联删除,
m为别名而已,
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o
飘过 学习
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哎，大家怎么深夜了还都在这混啊
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收藏下，学习下。
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学习
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mark
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插入自动编号http://topic.csdn.net/u/20080717/17/e304bdb6-d254-4ef5-878b-c6beb9609738.html
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declare @sql varchar(4000)
set @sql = ’select Name’
select @sql = @sql + ‘,sum(case Subject when ”’+Subject+”’ then Result end) [’+Subject+’]’
from (select distinct Subject from CJ) as a
select @sql = @sql+’ from test group by name’
exec(@sql)
行列转换–合并 [i][/i]
有表A,
id pid
1 1
1 2
1 3
2 1
2 2
3 1
如何化成表B:
id pid
1 1,2,3
2 1,2
3 1
创建一个合并的函数
create function fmerg(@id int)
returns varchar(8000)
as
begin
declare @str varchar(8000)
set @str=”
select @str=@str+’,'+cast(pid as varchar) from 表A where id=@id
set @str=right(@str,len(@str)-1)
return(@str)
End
go
–调用自定义函数得到结果
select distinct id,dbo.fmerg(id) from 表A
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学习 。。。
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学习
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学习+收藏+膜拜
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学习+接分
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学习+接分
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我要认真学习
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不用SQL语句照样去掉重复数据,在一个表中建一个非聚集、唯一值、忽略重复值的索引.....然后把源表数据导过去就OK
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好人还是比较多
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mark.
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learning
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学习
