SQL: which is better IN or OR

Question

Hi,
I have a query which is in the format:
select * from (
select col1, col2, col3
from tab1, tab2, tab3
where tab1.col1='aa' AND tab2.col2='BBB' ...
AND (tab1.col1='AA' OR tab1.col='BB' OR tab1.col='CC'... OR tab1.col='NN')
ORDER BY tab1.col3 DESC )
WHERE ROWNUM <= 500
(Please ignore the correctness of the query since I have simplified it)
My question is:
What is the difference in the performace between using OR with respect to using something like:
AND (tab1.col1 IN ('AA' , 'BB', 'CC'... ,'NN'))
Can someone please explain the difference in performace between using IN over OR?
Thanks,
- M

Answer 1

Check out the predicate information for both methods:
SQL> explain plan for
  2  select *
  3  from   dual
  4  where  dummy IN ('A','B','C','X','Y','Z');
Predicate Information (identified by operation id):
   1 - filter("DUAL"."DUMMY"='A' OR "DUAL"."DUMMY"='B' OR
              "DUAL"."DUMMY"='C' OR "DUAL"."DUMMY"='X' OR "DUAL"."DUMMY"='Y' OR
              "DUAL"."DUMMY"='Z')
SQL> explain plan for
  2  select *
  3  from   dual
  4  where (dummy = 'A'
  5      or dummy = 'B'
  6      or dummy = 'C'
  7      or dummy = 'X'
  8      or dummy = 'Y'
  9      or dummy = 'Z'
10        )
11  ;
Predicate Information (identified by operation id):
   1 - filter("DUAL"."DUMMY"='A' OR "DUAL"."DUMMY"='B' OR
              "DUAL"."DUMMY"='C' OR "DUAL"."DUMMY"='X' OR "DUAL"."DUMMY"='Y' OR
              "DUAL"."DUMMY"='Z')I think the IN version is a lot less typing and easier to maintain.