Other methods of writing such SQL

Question

Hi All,
Oracle 11g r2 version:
I tried to generate alphabet sequence like A-Z followed by AA-ZZ followed by AAA-ZZZ etc... using this query.
Can anybody suggest any other ways to do it in terms of BETTER performance.
WITH chrset AS
        (    SELECT CHR (ASCII ('A') + ROWNUM - 1) alph
               FROM DUAL
         CONNECT BY ROWNUM <= 26),
     t AS
        (SELECT alph FROM chrset
         UNION ALL
         SELECT a.alph || b.alph
           FROM chrset a, chrset b
         UNION ALL
         SELECT a.alph || b.alph || c.alph
           FROM chrset a, chrset b, chrset c
         UNION ALL
         SELECT a.alph || b.alph || c.alph || d.alph
           FROM chrset a,
                chrset b,
                chrset c,
                chrset d
         UNION ALL
         SELECT a.alph || b.alph || c.alph || d.alph || e.alph
           FROM chrset a,
                chrset b,
                chrset c,
                chrset d,
                chrset e),
     basetbl AS (SELECT ROWNUM r, alph FROM t)
SELECT r id, alph nm
  FROM basetbl
WHERE r <= 100;Cheers,
Manik.
Edited by: Manik on Mar 8, 2013 11:43 AM

Answer 1

select case when rownum <= 26 then chr (64 + rownum )
            when rownum <= 26*26 then
                 chr (64 + floor((rownum-1)/26) ) ||
                 chr (64 + decode(mod(rownum,26),0,26,mod(rownum,26)) )
       end  alph
from dual
connect by rownum <= 100;You can add to CASE if more than 26*26 is required..
Edited by: jeneesh on Mar 8, 2013 12:02 PM
Definitely more options are there - MODEL, RECURSION (With WITH clause).. You can try yourself and come back if you face any issues..