问Rank函数oracle sql

EN

select aid
       , email
       , trunc((rnk-1)/5) + 1 as pageno
from ( select aid
              , email
              , rank() over (order by post_date desc ) as rnk
       from ads )

row_number() over ( order by post_date desc, aid asc ) as rn

rank( expression1, ... expression_n ) WITHIN GROUP ( ORDER BY expression1, ... expression_n )

select rank(1000, 500) WITHIN GROUP (ORDER BY salary, bonus) from employees;