--按某一字段分组取最大(小)值所在行的数据
/*
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
*/
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
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
*/
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
*/
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
*/
/*
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
*/
/*
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
/*
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
*/
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
/*
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
/*
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
*/
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
/*
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,假如整行数据有重复,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
*/
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)
*/
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)
*/
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)
*/