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Home -> Community -> Usenet -> c.d.o.server -> Re: Performance of cascaded views ?
Michael Keppler wrote:
>
> Hello everybody !
>
> I'm a database programmer and I often have to use nearly equal queries
> to retrieve information from the database. So I thought about views. I
> could use a first view to select all articles from a catalog which are
> in the same group (for instance books) and a second view that will
> select all books from the first view that have a scientific theme.
>
> So I always could use a view, that uses a view, that uses a view and so
> on instead of writing select-statements with more than 100 rows.
>
> But what is with database performance? Is every view executed one by one
> and then the next one is executed on the result or does the optimizer
> make one big query from all of my views ?
>
> So can I make extended use of views to make my database programming
> easier or will I get a really bad performance that way ??
>
> Ciao and Thanks, Michael.
>
> --
> Michael.Keppler_at_bigfoot.com
Views of views of views aren't a problem per se...but it is important to recognise the difference between intergration and resolution.
Integration is when the database can merge the text of the view in with your query and thus run it as "one query"...
Resolution is when the database decides to go get all the rows as defined by your view, and THEN add additional where clauses, other views etc etc...This can sometimes be a bad thing obviosuly.
Resolution is probably most common when you join views that contain grouping expressions...
HTH
--
"Some days you're the pigeon, and some days you're the statue." Received on Fri Aug 06 1999 - 04:47:57 CDT
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