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Why my index is not used?

Bruce Jin
Ranch Hand

Joined: Sep 20, 2001
Posts: 666
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


BJ - SCJP and SCWCD
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Carol Enderlin
drifter
Ranch Hand

Joined: Oct 10, 2000
Posts: 1364
they should?
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Why my index is not used?