SQL Server 按某一字段分组取最大(小)值所在行的数据

-- 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) ' ),
( ' 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 ' )

-- 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

-- 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

-- 三、用开空函数row_number() over()
SELECT  * FROM (SELECT*,ROW_NUMBER() OVER( PARTITION BY name ORDER BY val DESC ) rid FROM  tb) AS t WHERE rid = 1