sql 语句 那位高手教下！！！
首先建表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')
在这表里面用sql语句查询
select a.* from tb a where not exists(select 1 from tb where name = a.name and val > a.val)
这里面的 1 是什么意思
select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name
也是 1 的问题
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 where val = (select top 1 val from tb where name = a.name order by newid()) order by a.name
这里面的newid()) 函数什么意思 怎么用
