Re: Oracle SQL question

In article <85d21k$bcg$1_at_nnrp1.deja.com>,   gweilo97_at_my-deja.com wrote:
>
> > the /*+ ..... */ indicates the force to use a certain method and
> > another hint is to use a bitmap index on columns where there are
just
> > a few possible distinct values like sex has probably three: M,F and
> > null, it will increase speed.
>
> Thanks for this. What happens if the index referred to doesn't
exist?
> Performance problems?
>

Nothing happens. The text inside /*+ ... */ (called a hint) is ignored unless it is syntactically and semantically accurate.

Performance problems? Only in the remotest circumstances. If you have queries identical to the above except without the hint, because they are syntactically not exactly the same, they cannot share the same SQL query in the SQL buffer. That wasn't clear, was it? Let's call the above query A, and the equivalent without the hint, B. Run A, and it will be stored (parsed) in the SQL buffer. Run B, and Oracle will look in the buffer for it, not find it, and load and parse it. This would have been avoided if B were exactly the same as A. Anyway, you probably don't have an equivalent query like B.

Salaam Yitbarek

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Before you buy. Received on Mon Jan 10 2000 - 12:18:58 CST