SQL to output line number in results of a query

Question

I would like to generate a line number for each line in the results of a sql query. How is it possible to do that?

Example: In the request

select di         


        

Answer 1

In Oracle

SQL> select row_number() over (order by deptno) as rn
  2         , deptno
  3  from
  4     ( select distinct deptno
  5            from emp
  6          )
  7  /

        RN     DEPTNO
---------- ----------
         1         10
         2         20
         3         30

SQL>