Re: QQQ

On 14 Jul 2005 10:29:12 -0700, soalvajavab1_at_yahoo.com wrote:

>Is calculations on an indexed column make index unused? is there any
>solution?

Yes. Has always been the case. Use function based indexes depending on version and edition
>
>Does UNION better than OR? what about NOT EXISTS and HAVING
>

Please read the performance and tuning manual for your version

>Is LIKE make index unused too? what we can do for that?

Please read the performance and tuning manual for your version

>
>What's the pros and cons of using subqueries instead of JOIN?

Please read the performance and tuning manual for your version

>
>Can we disable an index by concatenating a null or 0 to the column
>name?
>

Depending on version. The current versions of the CBO will notice the calculation is redundant and ignore it.

>if we need more that 20% of the rows in the table is FTS is better?

You could easily calculate the amount of I/O involved depending on actual statements
>
>what exactly bind variable help in performance? is it really bifg deal
>or not?

Quoting Thomas Kyte
If I would have to write a book on 'How to build an unscalable Oracle application', the first and last chapter would be entitled 'Do not use bind variables'

--
Sybrand Bakker, Senior Oracle DBA