On Mon, 2008-11-10 at 14:47 +0000, [EMAIL PROTECTED] wrote:
> > But joins are what relation databases excel at, so PHP would be the 
> 
> > bottleneck in your example.
> 
> 
> 
> Not always...
> 
> 
> 
> If your JOIN can not be easily constrained in the query, until some kind of 
> processing of the result set takes place, you can end up with a monster 
> interim result set that will swap the DB server, and send it to its knees.
> 
> 
> 
> For example, if you need a result set of 10 items, some of which (but not 
> all) relate to a second table, and the left outer join the generates millions 
> of rows...
> 
> 
> 
> Also:
> 
> 
> 
> SQL is great at many things.
> 
> 
> 
> But something like a tree traversal or other results that depend on the rows 
> returned can be a real bear, especially for pages that are not your core 
> scalable must-have part of the site -- Where you don't want to complicate 
> everything else for just this one admin/report page.
> 
> 
> 
> I'm only saying that, on occasion, the dozen DB calls wins out over a JOIN 
> that swaps madly.
> 
> 
> 
Then surely it is still a badly created query? If you're using PHP to
filter the results, even if it's in order to create a second query, your
SQL is not as good as it could be. The only thing that would benefit is
where a query needs information that is only available from outside the
database, which in turn is based on information from a query.


Ash
www.ashleysheridan.co.uk


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