Oracle SQL - Hvordan får man distinkte rækker ved hjælp af RANK() eller DENSE_RANK() eller ROW_NUMBER() analytiske funktion?

Hvis du bliver mere specifik i row_number , med partitioning by dept,salary så kan du kombinere row_number og dense_rank som i denne forespørgsel:

with data_row as 
( 
select 7839 as empno, 10 as deptno, 5000 as salary from dual union all
select 7782 as empno, 10 as deptno, 2450 as salary from dual union all
select 7934 as empno, 10 as deptno, 1300 as salary from dual union all
select 1111 as empno, 10 as deptno, 1111 as salary from dual union all
select 7935 as empno, 20 as deptno, 6000 as salary from dual union all
select 7788 as empno, 20 as deptno, 3000 as salary from dual union all
select 7902 as empno, 20 as deptno, 3000 as salary from dual union all
select 7566 as empno, 20 as deptno, 2975 as salary from dual union all
select 2222 as empno, 20 as deptno, 2222 as salary from dual union all
select 7698 as empno, 30 as deptno, 2850 as salary from dual union all
select 7499 as empno, 30 as deptno, 1600 as salary from dual union all
select 7844 as empno, 30 as deptno, 1500 as salary from dual union all
select 3333 as empno, 30 as deptno, 1333 as salary from dual
)
select *
from
(
select 
       deptno,
       salary,
       dense_rank() over (partition by deptno order by salary desc) as drank,
       row_number() over (partition by deptno, salary order by salary desc) as rowno             

from data_row
)
where drank <=3 and
      rowno =1