Re: No future for DB2 - slightly off-topic, discusses what people are being taught at uni

"rkusenet" <rkusenet_at_hotmail.com> wrote:

> So creating index on the FKY column
> should be automatic when creating the FKY constraint.

Not necessarily, at least AIUI.

Say one has a table person with fields title, first_name, last_name, add1, 2, 3.....

Now, you have title as a lookup table - it's a lookup into the title table.

Now, the vast bulk of your inserts will be Mr. or Ms., so you will get a skewed index and performance can suffer if you have an index, rather than doing a simple table scan.

I know that this has been an issue with Interbase in the past which automagically created (AIUI, one can now change this). I'm not sure of the performance implications for Oracle, but it is AFAICS, one good reason for not *_automatically_* creating an index.

Paul...

-- 

plinehan __at__ yahoo __dot__ __com__

XP Pro, SP 2, 

Oracle, 9.2.0.1.0 (Enterprise Ed.)
Interbase 6.0.1.0;

When asking database related questions, please give other posters 
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The exact text and/or number of error messages is useful (!= "it didn't work!").
Thanks.
 
Furthermore, as a courtesy to those who spend 
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do not top post.