Re: Bind Variables...

Thanks for being helpful as always Thomas

But i was under the assumption that when we use binds, the optimizer makes poor decisions compared to when it has the exact value since the optimizer puts pre- determined values to selectivity for the bind columns leading to a good (low) selectivity for the entire query.

From the little i know, different databases put an arbitary value for selectivity of 0.2 - 0.3 for the bind columns so as to favor the use of indexes . So if we use the bind when more than 15% of the rows of the table get retrieved, wont using the index might actually degrade performance. ( The 15% is the thumb rule, not always true). So wont the bind actually decrease performance if a large part of the table is retrieved?.

My brain is usually out for lunch and i may be totally wrong on this.

Pardon me for one small question out of this topic . Does the Ordering of columns matter in "Create Index". From the small test i conducted, it does not seem to matter. Celko says it may matter (Sql for Smarties). The other experts seem to be divided on this.

Thomas Kyte <tkyte_at_us.oracle.com> wrote in message news:<9sa2jc01oe4_at_drn.newsguy.com>...
> In article <9s9lm4$edf$1_at_innbox.cnet.com>, "Jack says...
> >
> >I have been debating the answer for this question.... but not really into a
> >solution,,,,
> >
> >When to and When not to use bind variables???
> >
>
> 99.999999% of the time -- use bind variables.
>
> In a datawarehouse, where you have computed histograms and have very skewed data
> -- skip the bind variable on that column -- sometimes.
>
> >When to and When not to placeholder columns(&) ?/
> >
>
> only when forced to.
>
> >Thanks
> >Jack....
> >
> >
> >
Received on Wed Nov 07 2001 - 02:30:37 CST