By using this site, you agree to our updated Privacy Policy and our Terms of Use. Manage your Cookies Settings.
438,322 Members | 1,182 Online
Bytes IT Community
+ Ask a Question
Need help? Post your question and get tips & solutions from a community of 438,322 IT Pros & Developers. It's quick & easy.

Inconsistant query results - Please help

P: n/a
Hi All,

I have a table Truck_Journey with the following structure

Tj_Date Date
Tj_Truck_Id Number(5)
Tj_Truck_No Varchar2(10)
Tj_Km Number(9)
....

If I give a
select distinct (tj_truck_no) from truck_journey where tj_truck_id is null;
it works and shows all the truck numbers where the truck id is null

If I create a non-unique index on tj_date + tj_truck_id then the above query
does not show any records. When I run an explain plan, it shows that it's
doing a index scan.

My queries are
1)According to the documentation (as I understand it), using a "is null" in
the select should do a full table scan. So how come it's doing an index
scan?

2)Whatever the scan methodology used, why is it showing an incorrect output
after adding the index? Does this have to do anything with any optimization
parameters or something?

Thanks in advance

Regards,
Bliss

Jul 19 '05 #1
Share this question for a faster answer!
Share on Google+

This discussion thread is closed

Replies have been disabled for this discussion.