SQL question

Howdy folks,

I have a file with about 1/2 million records on our development
machine (V4R2).

I ran a SQL query from ISQL:
-  Select distinct FIELD from FILE.
The query ran in about 2 minutes and gave me the result set with 
about 200,000 records. FIELD is not a key field.

I ran another query from ISQL over the same file/field:
- Select count(distinct FIELD) from FILE.
This query ran for over 10 minutes and returned the count.
Why would this query take so much longer than the first query? I ran the
test a few times when there was hardly any activity on the system and 
got the same results. The 2nd query takes atleast 5 times as long 
to complete. 
We have a similar table(few hundred thousand rcds)on an RS6000/Oracle
database. I ran similar queries over Oracle and there was no noticeable
difference in run times. I chose a non-indexed field.
What is so different about DB2/400 that would cause this? Just
curious...

Thanks

Ravi
+---
| This is the Midrange System Mailing List!
| To submit a new message, send your mail to MIDRANGE-L@midrange.com.
| To subscribe to this list send email to MIDRANGE-L-SUB@midrange.com.
| To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com.
| Questions should be directed to the list owner/operator: david@midrange.com
+---