Why my index is not used?

[Bruce Jin]

These 2 queries take 23 seconds on Oracle:

(1) select invline from mrcmpower.bisales order by invline desc
(2) select invline from mrcmpower.bisales where invline >0 order by invline desc

They should be the same because all 2 million rows in the table have invline > 0.

Then I added index: create index mrcmpower.index2 on mrcmpower.bisales (invline desc)

Now query (1) still takes 23 seconds and query (2) only takes 0.01 second.

Why query (1) does not use the index?

Thanks

[Carol Enderlin]

they should?