用SQL SERVER取分组数据第一条：查出每个班级的成绩第一名

create table test
(id int,
name varchar(10),
score int,
classname varchar(20));
 
insert into test values (1,\'张三\',100,\'一班\');
insert into test values (2,\'李四\',89,\'一班\');
insert into test values (3,\'王五\',97,\'一班\');
insert into test values (4,\'赵六\',87,\'二班\');
insert into test values (5,\'孙七\',94,\'二班\');
insert into test values (6,\'杨八\',76,\'二班\');

select t.* from
(select test.*,row_number() over (partition by classname order by score desc) rn 
from test) t
where rn=1;