最佳值行

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