Using SQL to check for duplicate records

Is there a more efficient way, using SQL, to check for duplicate records 
than the following?
SELECT A.IPROD, RRN(A) FROM IIM A
WHERE A.IPROD IN ( 
  SELECT B.IPROD FROM IIM B 
  GROUP BY B.IPROD 
  HAVING COUNT(*) > 1) 

It works fine on a 3 row dataset, with two of the rows being duplicates, 
or on a 3 row dataset with none of the rows being duplicates.  However on 
a table with 14,036 rows, and no duplicates, it takes forever.


Rob Berendt
-- 
"All creatures will make merry... under pain of death."
-Ming the Merciless (Flash Gordon)