SQL 相同记录 求时间最大值 最小值的问题

create table tb(A int,       B datetime)

insert into tb values(1 ,       '2008-1-10 ')

insert into tb values(1 ,       '2008-2-9') 

insert into tb values(1 ,       '2008-12-1') 

insert into tb values(2 ,       '2008-5-1') 

insert into tb values(2 ,       '2008-5-2') 

insert into tb values(3 ,       '2008-5-2')

go



select a , min(b) MinDate , max(b) MinDate  from tb group by a



/*

a           MinDate                                                MinDate                                                

----------- ------------------------------------------------------ ------------------------------------------------------ 

1           2008-01-10 00:00:00.000                                2008-12-01 00:00:00.000

2           2008-05-01 00:00:00.000                                2008-05-02 00:00:00.000

3           2008-05-02 00:00:00.000                                2008-05-02 00:00:00.000



（所影响的行数为 3 行）

*/



drop table tb 

SELECT A,MIN(B) AS MinDate,MAX(B) AS MaxDate FROM 表 GROUP BY A

select a , min(b) MinDate , max(b) MaxDate  from tb group by a

--处理表重复记录(查询和删除)

/******************************************************************************************************************************************************

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)

*/

select a,max(b) as b from tb group by a

create table tb(A int,       B datetime)

insert into tb values(1 ,       '2008-1-10 ')

insert into tb values(1 ,       '2008-2-9') 

insert into tb values(1 ,       '2008-12-1') 

insert into tb values(2 ,       '2008-5-1') 

insert into tb values(2 ,       '2008-5-2') 

insert into tb values(3 ,       '2008-5-2')

go



select a , min(b) MinDate , max(b) MinDate  from tb group by a



drop table tb 



/*

a           MinDate                                                MinDate                                                

----------- ------------------------------------------------------ ------------------------------------------------------ 

1           2008-01-10 00:00:00.000                                2008-12-01 00:00:00.000

2           2008-05-01 00:00:00.000                                2008-05-02 00:00:00.000

3           2008-05-02 00:00:00.000                                2008-05-02 00:00:00.000



（所影响的行数为 3 行）





*/

select a , min(a) , max(b) from tb group by a

SELECT A,MAX(B) AS MinDate,MIN(B) AS MaxDate FROM 表 GROUP BY A

SELECT

    A,

    MIN(B) AS MinDate,

    MAX(B) AS MaxDate

FROM tb

GROUP BY A

--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')

go



select * , px = identity(int,1,1) into tmp from tb



select 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')

go



select 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)

*/