oracle实现根据字段分组排序,取其第一条数据

select *
  from (select t.app_id,
               t.emp_no,
               t.device_id,
               t.device_type,
               t.last_connect_time,
               t.device_model,
               rank() over(partition by t.device_type order by t.last_connect_time desc) rankNo
          from table_name t) e
 where e.rankNo = 1;

rank() over(partition by e.commandid order by e.systemid desc) rankNo （
partition by 根据什么进行分组，
order by 根据什么进行排序,
rank() over() 进行排名
rankNo 别名
）

select * from (select t1.*,row_number() over(partition by t1.deptno order by hiredate desc) as row_number from emp t1) where row_number=1