Help tuning this query

Question

The tables are very large...
select a.number
from transaction a,
contr c,
directory b
where EXISTS ( SELECT 1
FROM contr D
WHERE D.CSSTATCHNG LIKE '%a'
AND D.SNCODE IN (3386, 3387)
AND D.COID = C.COID)
AND C.CSSTATCHNG LIKE '%a'
AND b.dnid = c.dnid
and a.snumber = b.dnnum
AND a.CDATE = SYSDATE - 90
AND ROWNUM <= 10
I only need 10 rows.
Note: I use Oracle 8.1.7
Thanks!

Answer 1

You really should analyze, even if you use a fairly small sample percent, it is usually better than no analyzing.
If the tables are large, you may want to try rephrasing the EXISTS as an IN, something like:
SELECT a.number
FROM transaction a, contr c, directory b
WHERE b.dnid = c.dnid and
      a.snumber = b.dnnum AND
      c.coid IN (SELECT coid
                 FROM contr d
                 WHERE d.csstatchng LIKE '%a' AND
                       d.sncode IN (3386, 3387)) AND
      c.csstatchng LIKE '%a' AND
      a.CDATE = SYSDATE - 90 AND
      ROWNUM <= 10or perhaps as a join to an in-line view like:
SELECT a.number
FROM transaction a, contr c, directory b,
     (SELECT coid FROM contr
      WHERE csstatchng LIKE '%a' AND
            sncode IN (3386, 3387)) d
WHERE b.dnid = c.dnid and
      a.snumber = b.dnnum AND
      c.coid = d.coid AND
      c.csstatchng LIKE '%a' AND
      a.CDATE = SYSDATE - 90 AND
      ROWNUM <= 10Although, I can't help feeling that you cuold skip that bit altogether and simply do:
SELECT a.number
FROM transaction a, contr c, directory b
WHERE b.dnid = c.dnid and
      a.snumber = b.dnnum AND
      c.sncode IN (3386, 3387) AND
      c.csstatchng LIKE '%a' AND
      a.CDATE = SYSDATE - 90 AND
      ROWNUM <= 10HTH
John