if not object_id('Tempdb..#T') is null drop table #T Go Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2)) Insert #T select 1,N'A',N'A1' union all select 2,N'A',N'A2' union all select 3,N'A',N'A3' union all select 4,N'B',N'B1' union all select 5,N'B',N'B2' Go --I、Name相同ID最小的记录(推荐用1,2,3),方法3在SQl05时,效率高于1、2 方法1: Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID<a.ID)方法2: select a.* from #T a join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID方法3: select * from #T a where ID=(select min(ID) from #T where Name=a.Name)方法4: select a.* from #T a join #T b on a.Name=b.Name and a.ID>=b.ID group by a.ID,a.Name,a.Memo having count(1)=1 方法5: select * from #T a group by ID,Name,Memo having ID=(select min(ID)from #T where Name=a.Name)方法6: select * from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)=0方法7: select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID)方法8: select * from #T a where ID!>all(select ID from #T where Name=a.Name)方法9(注:ID为唯一时可用): select * from #T a where ID in(select min(ID) from #T group by Name)--SQL2005:方法10: select ID,Name,Memo from (select *,min(ID)over(partition by Name) as MinID from #T a)T where ID=MinID方法11:select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID) as MinID from #T a)T where MinID=1生成结果: /* ID Name Memo ----------- ---- ---- 1 A A1 4 B B1(2 行受影响) */ --II、Name相同ID最大的记录,与min相反: 方法1: Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID>a.ID)方法2: select a.* from #T a join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID order by ID方法3: select * from #T a where ID=(select max(ID) from #T where Name=a.Name) order by ID方法4: select a.* from #T a join #T b on a.Name=b.Name and a.ID<=b.ID group by a.ID,a.Name,a.Memo having count(1)=1 方法5: select * from #T a group by ID,Name,Memo having ID=(select max(ID)from #T where Name=a.Name)方法6: select * from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)=0方法7: select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID desc)方法8: select * from #T a where ID!<all(select ID from #T where Name=a.Name)方法9(注:ID为唯一时可用): select * from #T a where ID in(select max(ID) from #T group by Name)--SQL2005:方法10: select ID,Name,Memo from (select *,max(ID)over(partition by Name) as MinID from #T a)T where ID=MinID方法11: select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID desc) as MinID from #T a)T where MinID=1生成结果2: /* ID Name Memo ----------- ---- ---- 3 A A3 5 B B2(2 行受影响) */--2、删除重复记录有大小关系时,保留大或小其中一个记录 --> --> (Roy)生成測試數據if not object_id('Tempdb..#T') is null drop table #T Go Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2)) Insert #T select 1,N'A',N'A1' union all select 2,N'A',N'A2' union all select 3,N'A',N'A3' union all select 4,N'B',N'B1' union all select 5,N'B',N'B2' Go--I、Name相同ID最小的记录(推荐用1,2,3),保留最小一条 方法1: delete a from #T a where exists(select 1 from #T where Name=a.Name and ID<a.ID)方法2: delete a from #T a left join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null方法3: delete a from #T a where ID not in (select min(ID) from #T where Name=a.Name)方法4(注:ID为唯一时可用): delete a from #T a where ID not in(select min(ID)from #T group by Name)方法5: delete a from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)>0方法6: delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID)方法7: delete a from #T a where ID>any(select ID from #T where Name=a.Name)select * from #T生成结果: /* ID Name Memo ----------- ---- ---- 1 A A1 4 B B1(2 行受影响) */ --II、Name相同ID保留最大的一条记录:方法1: delete a from #T a where exists(select 1 from #T where Name=a.Name and ID>a.ID)方法2: delete a from #T a left join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null方法3: delete a from #T a where ID not in (select max(ID) from #T where Name=a.Name)方法4(注:ID为唯一时可用): delete a from #T a where ID not in(select max(ID)from #T group by Name)方法5: delete a from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)>0方法6: delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID desc)方法7: delete a from #T a where ID<any(select ID from #T where Name=a.Name) select * from #T /* ID Name Memo ----------- ---- ---- 3 A A3 5 B B2(2 行受影响) */--3、删除重复记录没有大小关系时,处理重复值 --> --> (Roy)生成測試數據
if not object_id('Tempdb..#T') is null drop table #T Go Create table #T([Num] int,[Name] nvarchar(1)) Insert #T select 1,N'A' union all select 1,N'A' union all select 1,N'A' union all select 2,N'B' union all select 2,N'B' Go方法1: if object_id('Tempdb..#') is not null drop table # Select distinct * into # from #T--排除重复记录结果集生成临时表#truncate table #T--清空表insert #T select * from # --把临时表#插入到表#T中--查看结果 select * from #T/* Num Name ----------- ---- 1 A 2 B(2 行受影响) */--重新执行测试数据后用方法2 方法2:alter table #T add ID int identity--新增标识列 go delete a from #T a where exists(select 1 from #T where Num=a.Num and Name=a.Name and ID>a.ID)--只保留一条记录 go alter table #T drop column ID--删除标识列--查看结果 select * from #T/* Num Name ----------- ---- 1 A 2 B(2 行受影响)*/--重新执行测试数据后用方法3 方法3: declare Roy_Cursor cursor local for select count(1)-1,Num,Name from #T group by Num,Name having count(1)>1 declare @con int,@Num int,@Name nvarchar(1) open Roy_Cursor fetch next from Roy_Cursor into @con,@Num,@Name while @@Fetch_status=0 begin set rowcount @con; delete #T where Num=@Num and Name=@Name set rowcount 0; fetch next from Roy_Cursor into @con,@Num,@Name end close Roy_Cursor deallocate Roy_Cursor--查看结果 select * from #T /* Num Name ----------- ---- 1 A 2 B(2 行受影响) */
select t.* from tb t where 创建时间 = (select min(创建时间) from tb where id = t.id)
--按某一字段分组取最大(小)值所在行的数据 --(爱新觉罗.毓华(十八年风雨,守得冰山雪莲花开) 2007-10-23于浙江杭州) /* 数据如下: name val memo a 2 a2(a的第二个值) a 1 a1--a的第一个值 a 3 a3:a的第三个值 b 1 b1--b的第一个值 b 3 b3:b的第三个值 b 2 b2b2b2b2 b 4 b4b4 b 5 b5b5b5b5b5 */ --创建表并插入数据: create table tb(name varchar(10),val int,memo varchar(20)) insert into tb values('a', 2, 'a2(a的第二个值)') insert into tb values('a', 1, 'a1--a的第一个值') insert into tb values('a', 3, 'a3:a的第三个值') insert into tb values('b', 1, 'b1--b的第一个值') insert into tb values('b', 3, 'b3:b的第三个值') insert into tb values('b', 2, 'b2b2b2b2') insert into tb values('b', 4, 'b4b4') insert into tb values('b', 5, 'b5b5b5b5b5') go--一、按name分组取val最大的值所在行的数据。 --方法1: select a.* from tb a where val = (select max(val) from tb where name = a.name) order by a.name --方法2: select a.* from tb a where not exists(select 1 from tb where name = a.name and val > a.val) --方法3: select a.* from tb a,(select name,max(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name --方法4: select a.* from tb a inner join (select name , max(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name --方法5 select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name /* name val memo ---------- ----------- -------------------- a 3 a3:a的第三个值 b 5 b5b5b5b5b5 */--二、按name分组取val最小的值所在行的数据。 --方法1: select a.* from tb a where val = (select min(val) from tb where name = a.name) order by a.name --方法2: select a.* from tb a where not exists(select 1 from tb where name = a.name and val < a.val) --方法3: select a.* from tb a,(select name,min(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name --方法4: select a.* from tb a inner join (select name , min(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name --方法5 select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val < a.val) order by a.name /* name val memo ---------- ----------- -------------------- a 1 a1--a的第一个值 b 1 b1--b的第一个值 */--三、按name分组取第一次出现的行所在的数据。 select a.* from tb a where val = (select top 1 val from tb where name = a.name) order by a.name /* name val memo ---------- ----------- -------------------- a 2 a2(a的第二个值) b 1 b1--b的第一个值 */--四、按name分组随机取一条数据。 select a.* from tb a where val = (select top 1 val from tb where name = a.name order by newid()) order by a.name /* name val memo ---------- ----------- -------------------- a 1 a1--a的第一个值 b 5 b5b5b5b5b5 */--五、按name分组取最小的两个(N个)val select a.* from tb a where 2 > (select count(*) from tb where name = a.name and val < a.val ) order by a.name,a.val select a.* from tb a where val in (select top 2 val from tb where name=a.name order by val) order by a.name,a.val select a.* from tb a where exists (select count(*) from tb where name = a.name and val < a.val having Count(*) < 2) order by a.name,a.val /* name val memo ---------- ----------- -------------------- a 1 a1--a的第一个值 a 2 a2(a的第二个值) b 1 b1--b的第一个值 b 2 b2b2b2b2 */--六、按name分组取最大的两个(N个)val select a.* from tb a where 2 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name,a.val select a.* from tb a where val in (select top 2 val from tb where name=a.name order by val desc) order by a.name,a.val select a.* from tb a where exists (select count(*) from tb where name = a.name and val > a.val having Count(*) < 2) order by a.name , a.val /* name val memo ---------- ----------- -------------------- a 2 a2(a的第二个值) a 3 a3:a的第三个值 b 4 b4b4 b 5 b5b5b5b5b5 */ --七,如果整行数据有重复,所有的列都相同。 /* 数据如下: name val memo a 2 a2(a的第二个值) a 1 a1--a的第一个值 a 1 a1--a的第一个值 a 3 a3:a的第三个值 a 3 a3:a的第三个值 b 1 b1--b的第一个值 b 3 b3:b的第三个值 b 2 b2b2b2b2 b 4 b4b4 b 5 b5b5b5b5b5 */ --在sql server 2000中只能用一个临时表来解决,生成一个自增列,先对val取最大或最小,然后再通过自增列来取数据。 --创建表并插入数据: create table tb(name varchar(10),val int,memo varchar(20)) insert into tb values('a', 2, 'a2(a的第二个值)') insert into tb values('a', 1, 'a1--a的第一个值') insert into tb values('a', 1, 'a1--a的第一个值') insert into tb values('a', 3, 'a3:a的第三个值') insert into tb values('a', 3, 'a3:a的第三个值') insert into tb values('b', 1, 'b1--b的第一个值') insert into tb values('b', 3, 'b3:b的第三个值') insert into tb values('b', 2, 'b2b2b2b2') insert into tb values('b', 4, 'b4b4') insert into tb values('b', 5, 'b5b5b5b5b5') goselect * , px = identity(int,1,1) into tmp from tbselect m.name,m.val,m.memo from ( select t.* from tmp t where val = (select min(val) from tmp where name = t.name) ) m where px = (select min(px) from ( select t.* from tmp t where val = (select min(val) from tmp where name = t.name) ) n where n.name = m.name)drop table tb,tmp/* name val memo ---------- ----------- -------------------- a 1 a1--a的第一个值 b 1 b1--b的第一个值(2 行受影响) */ --在sql server 2005中可以使用row_number函数,不需要使用临时表。 --创建表并插入数据: create table tb(name varchar(10),val int,memo varchar(20)) insert into tb values('a', 2, 'a2(a的第二个值)') insert into tb values('a', 1, 'a1--a的第一个值') insert into tb values('a', 1, 'a1--a的第一个值') insert into tb values('a', 3, 'a3:a的第三个值') insert into tb values('a', 3, 'a3:a的第三个值') insert into tb values('b', 1, 'b1--b的第一个值') insert into tb values('b', 3, 'b3:b的第三个值') insert into tb values('b', 2, 'b2b2b2b2') insert into tb values('b', 4, 'b4b4') insert into tb values('b', 5, 'b5b5b5b5b5') goselect m.name,m.val,m.memo from ( select * , px = row_number() over(order by name , val) from tb ) m where px = (select min(px) from ( select * , px = row_number() over(order by name , val) from tb ) n where n.name = m.name)drop table tb/* name val memo ---------- ----------- -------------------- a 1 a1--a的第一个值 b 1 b1--b的第一个值(2 行受影响) */
create table tb(ID int , 等级 varchar(10),创建时间 datetime) insert into tb values(24 , 'A级' , '2008-10-20 15:30:21') insert into tb values(25 , 'B级' , '2008-10-20 15:31:21') insert into tb values(32 , 'A级' , '2008-10-20 15:31:21') insert into tb values(33 , 'B级' , '2008-10-20 15:38:21') insert into tb values(24 , 'B级' , '2008-10-21 15:31:21') insert into tb values(32 , 'C级' , '2008-10-21 17:31:21') insert into tb values(32 , 'C级' , '2008-10-22 9:31:21') insert into tb values(45 , 'A级' , '2008-10-23 15:31:21') insert into tb values(45 , 'B级' , '2008-10-23 18:21:21') goselect t.* from tb t where 创建时间 = (select min(创建时间) from tb where id = t.id) order by t.id /* ID 等级 创建时间 ----------- ---------- ------------------------------------------------------ 24 A级 2008-10-20 15:30:21.000 25 B级 2008-10-20 15:31:21.000 32 A级 2008-10-20 15:31:21.000 33 B级 2008-10-20 15:38:21.000 45 A级 2008-10-23 15:31:21.000(所影响的行数为 5 行) */select t.* from tb t where not exists (select 1 from tb where id = t.id and 创建时间 < t.创建时间) order by t.id /* ID 等级 创建时间 ----------- ---------- ------------------------------------------------------ 24 A级 2008-10-20 15:30:21.000 25 B级 2008-10-20 15:31:21.000 32 A级 2008-10-20 15:31:21.000 33 B级 2008-10-20 15:38:21.000 45 A级 2008-10-23 15:31:21.000(所影响的行数为 5 行) */drop table tb
select A.[ID] ,A.等级 ,... --要选取得字段 B.创建时间 from 表 A inner join 表 B on A.[ID] = B.[ID] where not exists(select 1 from 表 where [ID] = B.[ID] and 创建时间>B.创建时间)
楼主朋友,我有点想复杂了。可以用下面的代码 select A.* from 表 A where not exists(select 1 from 表 where [ID] = A.[ID] and 创建时间>A.创建时间)
create table tb(ID int , 等级 varchar(10),创建时间 datetime) insert into tb values(24 , 'A级' , '2008-10-20 15:30:21') insert into tb values(25 , 'B级' , '2008-10-20 15:31:21') insert into tb values(32 , 'A级' , '2008-10-20 15:31:21') insert into tb values(33 , 'B级' , '2008-10-20 15:38:21') insert into tb values(24 , 'B级' , '2008-10-21 15:31:21') insert into tb values(32 , 'C级' , '2008-10-21 17:31:21') insert into tb values(32 , 'C级' , '2008-10-22 9:31:21') insert into tb values(45 , 'A级' , '2008-10-23 15:31:21') insert into tb values(45 , 'B级' , '2008-10-23 18:21:21')delete a from ( select * ,rn = row_number() over (partition by id order by 创建时间 desc)from tb )a where rn >1select * from tbID 等级 创建时间 ----------- ---------- ----------------------- 25 B级 2008-10-20 15:31:21.000 33 B级 2008-10-20 15:38:21.000 24 B级 2008-10-21 15:31:21.000 32 C级 2008-10-22 09:31:21.000 45 B级 2008-10-23 18:21:21.000(5 行受影响)
/******************************************************************************************************************************************************
1、Num、Name相同的重复值记录,没有大小关系只保留一条
2、Name相同,ID有大小关系时,保留大或小其中一个记录
整理人:中国风(Roy)日期:2008.06.06
******************************************************************************************************************************************************/--1、用于查询重复处理记录(如果列没有大小关系时2000用生成自增列和临时表处理,SQL2005用row_number函数处理)--> --> (Roy)生成測試數據
if not object_id('Tempdb..#T') is null
drop table #T
Go
Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))
Insert #T
select 1,N'A',N'A1' union all
select 2,N'A',N'A2' union all
select 3,N'A',N'A3' union all
select 4,N'B',N'B1' union all
select 5,N'B',N'B2'
Go
--I、Name相同ID最小的记录(推荐用1,2,3),方法3在SQl05时,效率高于1、2
方法1:
Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID<a.ID)方法2:
select a.* from #T a join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID方法3:
select * from #T a where ID=(select min(ID) from #T where Name=a.Name)方法4:
select a.* from #T a join #T b on a.Name=b.Name and a.ID>=b.ID group by a.ID,a.Name,a.Memo having count(1)=1 方法5:
select * from #T a group by ID,Name,Memo having ID=(select min(ID)from #T where Name=a.Name)方法6:
select * from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)=0方法7:
select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID)方法8:
select * from #T a where ID!>all(select ID from #T where Name=a.Name)方法9(注:ID为唯一时可用):
select * from #T a where ID in(select min(ID) from #T group by Name)--SQL2005:方法10:
select ID,Name,Memo from (select *,min(ID)over(partition by Name) as MinID from #T a)T where ID=MinID方法11:select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID) as MinID from #T a)T where MinID=1生成结果:
/*
ID Name Memo
----------- ---- ----
1 A A1
4 B B1(2 行受影响)
*/
--II、Name相同ID最大的记录,与min相反:
方法1:
Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID>a.ID)方法2:
select a.* from #T a join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID order by ID方法3:
select * from #T a where ID=(select max(ID) from #T where Name=a.Name) order by ID方法4:
select a.* from #T a join #T b on a.Name=b.Name and a.ID<=b.ID group by a.ID,a.Name,a.Memo having count(1)=1 方法5:
select * from #T a group by ID,Name,Memo having ID=(select max(ID)from #T where Name=a.Name)方法6:
select * from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)=0方法7:
select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID desc)方法8:
select * from #T a where ID!<all(select ID from #T where Name=a.Name)方法9(注:ID为唯一时可用):
select * from #T a where ID in(select max(ID) from #T group by Name)--SQL2005:方法10:
select ID,Name,Memo from (select *,max(ID)over(partition by Name) as MinID from #T a)T where ID=MinID方法11:
select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID desc) as MinID from #T a)T where MinID=1生成结果2:
/*
ID Name Memo
----------- ---- ----
3 A A3
5 B B2(2 行受影响)
*/--2、删除重复记录有大小关系时,保留大或小其中一个记录
--> --> (Roy)生成測試數據if not object_id('Tempdb..#T') is null
drop table #T
Go
Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))
Insert #T
select 1,N'A',N'A1' union all
select 2,N'A',N'A2' union all
select 3,N'A',N'A3' union all
select 4,N'B',N'B1' union all
select 5,N'B',N'B2'
Go--I、Name相同ID最小的记录(推荐用1,2,3),保留最小一条
方法1:
delete a from #T a where exists(select 1 from #T where Name=a.Name and ID<a.ID)方法2:
delete a from #T a left join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null方法3:
delete a from #T a where ID not in (select min(ID) from #T where Name=a.Name)方法4(注:ID为唯一时可用):
delete a from #T a where ID not in(select min(ID)from #T group by Name)方法5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)>0方法6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID)方法7:
delete a from #T a where ID>any(select ID from #T where Name=a.Name)select * from #T生成结果:
/*
ID Name Memo
----------- ---- ----
1 A A1
4 B B1(2 行受影响)
*/
--II、Name相同ID保留最大的一条记录:方法1:
delete a from #T a where exists(select 1 from #T where Name=a.Name and ID>a.ID)方法2:
delete a from #T a left join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null方法3:
delete a from #T a where ID not in (select max(ID) from #T where Name=a.Name)方法4(注:ID为唯一时可用):
delete a from #T a where ID not in(select max(ID)from #T group by Name)方法5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)>0方法6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID desc)方法7:
delete a from #T a where ID<any(select ID from #T where Name=a.Name)
select * from #T
/*
ID Name Memo
----------- ---- ----
3 A A3
5 B B2(2 行受影响)
*/--3、删除重复记录没有大小关系时,处理重复值
--> --> (Roy)生成測試數據
if not object_id('Tempdb..#T') is null
drop table #T
Go
Create table #T([Num] int,[Name] nvarchar(1))
Insert #T
select 1,N'A' union all
select 1,N'A' union all
select 1,N'A' union all
select 2,N'B' union all
select 2,N'B'
Go方法1:
if object_id('Tempdb..#') is not null
drop table #
Select distinct * into # from #T--排除重复记录结果集生成临时表#truncate table #T--清空表insert #T select * from # --把临时表#插入到表#T中--查看结果
select * from #T/*
Num Name
----------- ----
1 A
2 B(2 行受影响)
*/--重新执行测试数据后用方法2
方法2:alter table #T add ID int identity--新增标识列
go
delete a from #T a where exists(select 1 from #T where Num=a.Num and Name=a.Name and ID>a.ID)--只保留一条记录
go
alter table #T drop column ID--删除标识列--查看结果
select * from #T/*
Num Name
----------- ----
1 A
2 B(2 行受影响)*/--重新执行测试数据后用方法3
方法3:
declare Roy_Cursor cursor local for
select count(1)-1,Num,Name from #T group by Num,Name having count(1)>1
declare @con int,@Num int,@Name nvarchar(1)
open Roy_Cursor
fetch next from Roy_Cursor into @con,@Num,@Name
while @@Fetch_status=0
begin
set rowcount @con;
delete #T where Num=@Num and Name=@Name
set rowcount 0;
fetch next from Roy_Cursor into @con,@Num,@Name
end
close Roy_Cursor
deallocate Roy_Cursor--查看结果
select * from #T
/*
Num Name
----------- ----
1 A
2 B(2 行受影响)
*/
--按某一字段分组取最大(小)值所在行的数据
--(爱新觉罗.毓华(十八年风雨,守得冰山雪莲花开) 2007-10-23于浙江杭州)
/*
数据如下:
name val memo
a 2 a2(a的第二个值)
a 1 a1--a的第一个值
a 3 a3:a的第三个值
b 1 b1--b的第一个值
b 3 b3:b的第三个值
b 2 b2b2b2b2
b 4 b4b4
b 5 b5b5b5b5b5
*/
--创建表并插入数据:
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二个值)')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('b', 1, 'b1--b的第一个值')
insert into tb values('b', 3, 'b3:b的第三个值')
insert into tb values('b', 2, 'b2b2b2b2')
insert into tb values('b', 4, 'b4b4')
insert into tb values('b', 5, 'b5b5b5b5b5')
go--一、按name分组取val最大的值所在行的数据。
--方法1:
select a.* from tb a where val = (select max(val) from tb where name = a.name) order by a.name
--方法2:
select a.* from tb a where not exists(select 1 from tb where name = a.name and val > a.val)
--方法3:
select a.* from tb a,(select name,max(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name
--方法4:
select a.* from tb a inner join (select name , max(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name
--方法5
select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name
/*
name val memo
---------- ----------- --------------------
a 3 a3:a的第三个值
b 5 b5b5b5b5b5
*/--二、按name分组取val最小的值所在行的数据。
--方法1:
select a.* from tb a where val = (select min(val) from tb where name = a.name) order by a.name
--方法2:
select a.* from tb a where not exists(select 1 from tb where name = a.name and val < a.val)
--方法3:
select a.* from tb a,(select name,min(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name
--方法4:
select a.* from tb a inner join (select name , min(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name
--方法5
select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val < a.val) order by a.name
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值
*/--三、按name分组取第一次出现的行所在的数据。
select a.* from tb a where val = (select top 1 val from tb where name = a.name) order by a.name
/*
name val memo
---------- ----------- --------------------
a 2 a2(a的第二个值)
b 1 b1--b的第一个值
*/--四、按name分组随机取一条数据。
select a.* from tb a where val = (select top 1 val from tb where name = a.name order by newid()) order by a.name
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 5 b5b5b5b5b5
*/--五、按name分组取最小的两个(N个)val
select a.* from tb a where 2 > (select count(*) from tb where name = a.name and val < a.val ) order by a.name,a.val
select a.* from tb a where val in (select top 2 val from tb where name=a.name order by val) order by a.name,a.val
select a.* from tb a where exists (select count(*) from tb where name = a.name and val < a.val having Count(*) < 2) order by a.name,a.val
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
a 2 a2(a的第二个值)
b 1 b1--b的第一个值
b 2 b2b2b2b2
*/--六、按name分组取最大的两个(N个)val
select a.* from tb a where 2 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name,a.val
select a.* from tb a where val in (select top 2 val from tb where name=a.name order by val desc) order by a.name,a.val
select a.* from tb a where exists (select count(*) from tb where name = a.name and val > a.val having Count(*) < 2) order by a.name , a.val
/*
name val memo
---------- ----------- --------------------
a 2 a2(a的第二个值)
a 3 a3:a的第三个值
b 4 b4b4
b 5 b5b5b5b5b5
*/
--七,如果整行数据有重复,所有的列都相同。
/*
数据如下:
name val memo
a 2 a2(a的第二个值)
a 1 a1--a的第一个值
a 1 a1--a的第一个值
a 3 a3:a的第三个值
a 3 a3:a的第三个值
b 1 b1--b的第一个值
b 3 b3:b的第三个值
b 2 b2b2b2b2
b 4 b4b4
b 5 b5b5b5b5b5
*/
--在sql server 2000中只能用一个临时表来解决,生成一个自增列,先对val取最大或最小,然后再通过自增列来取数据。
--创建表并插入数据:
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二个值)')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('b', 1, 'b1--b的第一个值')
insert into tb values('b', 3, 'b3:b的第三个值')
insert into tb values('b', 2, 'b2b2b2b2')
insert into tb values('b', 4, 'b4b4')
insert into tb values('b', 5, 'b5b5b5b5b5')
goselect * , px = identity(int,1,1) into tmp from tbselect m.name,m.val,m.memo from
(
select t.* from tmp t where val = (select min(val) from tmp where name = t.name)
) m where px = (select min(px) from
(
select t.* from tmp t where val = (select min(val) from tmp where name = t.name)
) n where n.name = m.name)drop table tb,tmp/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值(2 行受影响)
*/
--在sql server 2005中可以使用row_number函数,不需要使用临时表。
--创建表并插入数据:
create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a', 2, 'a2(a的第二个值)')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 1, 'a1--a的第一个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('a', 3, 'a3:a的第三个值')
insert into tb values('b', 1, 'b1--b的第一个值')
insert into tb values('b', 3, 'b3:b的第三个值')
insert into tb values('b', 2, 'b2b2b2b2')
insert into tb values('b', 4, 'b4b4')
insert into tb values('b', 5, 'b5b5b5b5b5')
goselect m.name,m.val,m.memo from
(
select * , px = row_number() over(order by name , val) from tb
) m where px = (select min(px) from
(
select * , px = row_number() over(order by name , val) from tb
) n where n.name = m.name)drop table tb/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值(2 行受影响)
*/
insert into tb values(24 , 'A级' , '2008-10-20 15:30:21')
insert into tb values(25 , 'B级' , '2008-10-20 15:31:21')
insert into tb values(32 , 'A级' , '2008-10-20 15:31:21')
insert into tb values(33 , 'B级' , '2008-10-20 15:38:21')
insert into tb values(24 , 'B级' , '2008-10-21 15:31:21')
insert into tb values(32 , 'C级' , '2008-10-21 17:31:21')
insert into tb values(32 , 'C级' , '2008-10-22 9:31:21')
insert into tb values(45 , 'A级' , '2008-10-23 15:31:21')
insert into tb values(45 , 'B级' , '2008-10-23 18:21:21')
goselect t.* from tb t where 创建时间 = (select min(创建时间) from tb where id = t.id) order by t.id
/*
ID 等级 创建时间
----------- ---------- ------------------------------------------------------
24 A级 2008-10-20 15:30:21.000
25 B级 2008-10-20 15:31:21.000
32 A级 2008-10-20 15:31:21.000
33 B级 2008-10-20 15:38:21.000
45 A级 2008-10-23 15:31:21.000(所影响的行数为 5 行)
*/select t.* from tb t where not exists (select 1 from tb where id = t.id and 创建时间 < t.创建时间) order by t.id
/*
ID 等级 创建时间
----------- ---------- ------------------------------------------------------
24 A级 2008-10-20 15:30:21.000
25 B级 2008-10-20 15:31:21.000
32 A级 2008-10-20 15:31:21.000
33 B级 2008-10-20 15:38:21.000
45 A级 2008-10-23 15:31:21.000(所影响的行数为 5 行)
*/drop table tb
A.[ID]
,A.等级
,... --要选取得字段
B.创建时间
from
表 A
inner join
表 B
on
A.[ID] = B.[ID]
where
not exists(select 1 from 表 where [ID] = B.[ID] and 创建时间>B.创建时间)
select
A.*
from
表 A
where
not exists(select 1 from 表 where [ID] = A.[ID] and 创建时间>A.创建时间)
insert into tb values(24 , 'A级' , '2008-10-20 15:30:21')
insert into tb values(25 , 'B级' , '2008-10-20 15:31:21')
insert into tb values(32 , 'A级' , '2008-10-20 15:31:21')
insert into tb values(33 , 'B级' , '2008-10-20 15:38:21')
insert into tb values(24 , 'B级' , '2008-10-21 15:31:21')
insert into tb values(32 , 'C级' , '2008-10-21 17:31:21')
insert into tb values(32 , 'C级' , '2008-10-22 9:31:21')
insert into tb values(45 , 'A级' , '2008-10-23 15:31:21')
insert into tb values(45 , 'B级' , '2008-10-23 18:21:21')delete a
from
(
select * ,rn = row_number() over (partition by id order by 创建时间 desc)from tb
)a
where rn >1select * from tbID 等级 创建时间
----------- ---------- -----------------------
25 B级 2008-10-20 15:31:21.000
33 B级 2008-10-20 15:38:21.000
24 B级 2008-10-21 15:31:21.000
32 C级 2008-10-22 09:31:21.000
45 B级 2008-10-23 18:21:21.000(5 行受影响)