Re: Views on Views

In article <328BD999.118B_at_interlog.com>,

        John Parrott <spo_at_interlog.com> writes:
> I'm looking for pros and cons of using views.
>
> Suppose I create a complex view on a large table.
>
> Then I issue a statement like:
> select * from newview
> where field1 = XXXX
>
> Does the server first execute the statement in the view against the
> entire table then perform the second select statement which might limit
> the number of rows dramatically or is the server smart enough to limit
> the rows first then perform the functions in the view only on the
> limited result set.
>

That depends entirely on the quality of the query optimiser of the DBMS you're using. Similar questions can be asked for SQl queries not involving any view definitions. Although may smart optimisation techniques have been suggested in research, it is commonly known that the quality of query optimisers of commercial DBMSs varies strongly.

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