Parttion by 关键字是Oracle中分析性函数的一部分，它和聚合函数不同的地方在于它能够返回一个分组中的多条记录，儿聚合函数一般
row_number() over(partition by deptid order by salary) my_rank ,deptid,USERID,salary from tsaler; rank() over(partition by deptid order by salary) my_rank,deptid,USERID,salary from tsaler; dense_rank() over(partition by deptid order by salary) my_rank,deptid,USERID,salary from tsaler; (; (;
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