Oracle 10 g -SQL

Question

如何找到emp表中每個部門的前2名工資？

Emp Table 
----------- 
Row_id Salary Dept 
R1  2000 D1 
R2  3000 D1 
R3  4000 D1 
R4  5000 D1 
R5  2000 D2 
R6  3000 D2 
R7  4000 D2 
R8  5000 D2 

Answer 1

select 
    row_id,salary,dept 
from 
(
select 
    row_number() over (partition by dept order by salary desc) as sno, 
    row_id,salary,dept 
from emp 
) t 
where sno<=2 

Answer 2

請儘量將

select T1.Dept,T2.Salary 
from Emp_Table T1 join Emp_Table T2 
on T1.Dept=T2.Dept 
and T1.Salary>=T2.Salary 
group by T1.Dept,T2.Salary 
having COUNT(*) <=2