# 分组排序取最大、最小、最新、前N条记录

create table tb(name varchar(10),val int,memo varchar(20))

insert into tb values('a',    2,   'a2')

insert into tb values('a',    1,   'a1')

insert into tb values('a',    3,   'a3')

insert into tb values('b',    1,   'b1')

insert into tb values('b',    3,   'b3')

insert into tb values('b',    2,   'b2')

insert into tb values('b',    4,   'b4')

insert into tb values('b',    5,   'b5')

 name val memo a 2 a2 a 1 a1 a 3 a3 b 1 b1 b 3 b3 b 2 b2 b 4 b4 b 5 b5

name分组取val最大的值所在行的数据

select a.* from tb a where val = (select max(val) from tb where name = a.name) order by a.name

select a.* from tb a where not exists(select 1 from tb where name = a.name and val > a.val)

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

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

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 b 5 b5

name分组取val最小的值所在行的数据

select a.* from tb a where val = (select min(val) from tb where name = a.name) order by a.name

select a.* from tb a where not exists(select 1 from tb where name = a.name and val < a.val)

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

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

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 b 1 b1

name分组取第一次出现的行所在的数据

sql如下：

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 b 1 b1

name分组随机取一条数据

sql如下：

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 b 3 b3

name分组取最小的两个(N)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 2 a2 b 1 b1 b 2 b2

name分组取最大的两个(N)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 3 a3 a 2 a2 b 5 b5 b 4 b4