Paging data using rownum

Question

I am trying to fetch a range of data using rownum.
1. This select statmenet works
SELECT * from (SELECT id, name, seq from test order by seq desc) where rownum>=1 and rownum<=15
2. This select statmenet does not work
SELECT * from (SELECT id, name, seq from test order by seq desc) where rownum>=3 and rownum<=15
3. This select statment returns wrong rows
SELECT * from (SELECT id, name, seq, rownum as rn from test order by seq desc) where rn>=3 and rn<=15
4. This works, but two level deep
SELECT * from (SELECT id, name, seq, rownum as rn from (SELECT id, name, seq from test order by seq desc)) where rn>=3 and rn<=15
Is there a better way to fetch a range od data?
Thanks
YI

Answer 1

Generally, we do'nt need the query output based upon rownum because Rownum is determined after the complete resultset has been retrieved, but still if you need the query output based upon Rownum it should be something like this :
SCOTT@orcl> select empno,rownum from emp;
     EMPNO     ROWNUM
        10          1
      7499          2
      7521          3
      7566          4
      7654          5
      7698          6
      7782          7
      7788          8
      7839          9
      7844         10
      7876         11
     EMPNO     ROWNUM
      7900         12
      7902         13
      7934         14
      9999         15
15 rows selected.
SCOTT@orcl> ed
Wrote file afiedt.buf
  1  select * from ( select empno, row_number() over (order by empno) rorder from emp)
  2* where rorder between 2 and 4
SCOTT@orcl> /
     EMPNO     RORDER
      7499          2
      7521          3
      7566          4
SCOTT@orcl>Regards
Girish harma
Edited by: Girish Sharma on Mar 26, 2011 5:17 PM