Re: Index usage

You answered your own question.

ta.c3 is a nonindexed column, this means that the only way to satisfy the predicate is to perform a full table scan. Since this predicate condition forces a full table scan on ta, which will retrieve the ta.c1 column values at the same time, there is no need to use an index. In fact, an additional index access would decrease the query performance.

Daniel Fink

bhabani s pradhan wrote:

> Hi All,
>
> Merry Christmas to all.
>
> I have this interesting problem..
>
> For this query index ind1 on (c1,c2) columns is getting used.
> SELECT 'x'
> FROM tab ta
> WHERE ta.c1='val1';
> (gives index ind1 range scan)
>
> But for
>
> SELECT 'x'
> FROM tab ta
> WHERE ta.c1='val1'
> AND ta.c3 = 'val2';
> (gives FTS)
> index ind1 is not being used. c3 is a nonindexed column.
>
> I have already tried index(ta ind1) , RULE hints.
>
> The table and the index are analyzed.
>
> What cud be the reason for that?
>
> Regards,
> B S Pradhan

-- 
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-- 
Author: Daniel W. Fink
  INET: Daniel.Fink_at_Sun.COM

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