row_number rank dense_rank函数

一个sql看清这三个函数的区别：

SQL> select 
  2  dname,
  3  ename,
  4  sal,
  5  row_number() over(partition by dname order by sal desc) as row_number,
  6  rank() over(partition by dname order by sal desc) as rank_umber,
  7  dense_rank() over(partition by dname order by sal desc) as denserank_number
  8  from goolen
  9  order by 1,3 desc;

--注意观察红框里的信息：