Re: which column type char,varchar2 is better for index?

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Jonathan Lewis

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"Mark D Powell" <Mark.Powell_at_eds.com> wrote in message
news:2687bb95.0406110545.e66f62f_at_posting.google.com...


>

> When you test number verse varchar2 you should find very little

> practical difference though numeric key access should prove to be a

> little faster.  At least it did when an Oracle support analyst posted

> some test results a couple years back.

>


There are two different scenarios, though.

The speed of accessing a given amount of data, and
the estimated cardinality for the where clause that
is supposed to identify the data.

Representing numeric (or date) information as
character columns can cause the optimiser to
get wildly inaccurate estimates of cardinality
and therefore choose the wrong execution
path. (Which brings you back to the performance
question from a different direction).