Posted by Alexander Kuznetsov on 06/11/06 03:06

I'd like to repeat the suggestion to do your own experimenting. The
technology evolves quite fast, so anything you might have read in any
book / article / whatever esle may be already obsolete. The optimizer
is way smarter now than it used to be 5 or 10 years ago. In this
particular case you did not need to read anything, you could just take
any table of, say, 100K rows, with, say, 20 columns, create an index on
it

create index i1 on t1(col1, col2)

and see the execution plan for the query

select col1, col2 from t1 where col2 =....

That's all it takes, it's that simple.

Good luck!

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