Re: Creating Table as select...

Daniel Morgan <damorgan_at_x.washington.edu> wrote in message news:<1076312809.350235_at_yasure>...
> KDB wrote:
>
> > Hi Daniel,
> > I read the following in oracle 10g concepts manual:
> >
> > http://download-west.oracle.com/docs/cd/B12037_01/server.101/b10743/schema.htm#sthref893
> >
> > <Oracle10gConcepts>
> >
> > Unique and Nonunique Indexes
> > Indexes can be unique or nonunique. Unique indexes guarantee that no
> > two rows of a table have duplicate values in the key column (or
> > columns). Nonunique indexes do not impose this restriction on the
> > column values.
> >
> > Oracle recommends that unique indexes be created explicitly, and not
> > through enabling a unique constraint on a table.
> >
> > </Oracle10gConcepts>
> >
> > Can you please comment on this!
> >
> > --KDB
>
> Don't mind at all Howard. But my answer will be a bit less kind.
>
> Whoever wrote that has little or no experience in the real-world. They
> are an Oracle employee creating documentation and likely have never had
> the experience of creating or managing applications in the real-world.

This brings up an interesting point. A large vendor like O is going to have a lot of specialization, and I wouldn't expect too many DBA's from the real world would want to work at writing docs (aot books or advice columns :-). I would expect they use technically oriented writers. I would expect they have a review process for the docs (the bloopers are difficult to find these days). They have a corrections process.

So while your statement may be accurate, I don't think the expectations are realistic. O should fix the review process (unless there is a metric that shows this is a rare and declining problem, which is the general opinion I have of the docs).

>
> If you are going to create a unique index by all means follow the above
> advice. A better question is why create one at all? You gain nothing.
> You lose a lot.
>
> BTW: The question of unique index vs. unique constraint is one I
> routinely ask during job interviews. Those that don't know the
> difference don't get hired.

Wonders how many false negatives you get, given how an experienced person may know every detail and consequence of CREATE statements while implementing a system (or studying for an exam), but after six months of doing something else may not remember some details without reviewing tasks appropriate to the project.

jg

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