Wouldn't this involved a sub-query?
i.e.
select * from images where
( select * from categories where cat_id = 3 AND cat_id != 5)
Now, the question is, do the more recent versions of mysql support
subqueries?
Take a look at:
http://www.mysql.com/documentation/mysql/bychapter/manual_Introduction.html#ANSI_diff_Sub-selects
This may help you out in potentially re-writting your query?
possibly:
select images.* from images LEFT JOIN categories on images.id =
categories.id where categories.cat = 3 AND catdgories.cat != 5
HTH
-Brad
David Freeman wrote:
> Hi All
>
> This is probably off-topic here and my only real excuse is that after
> having searched google as well as both php and mysql sites/manuals I'm
> no closer to an answer for something I'd like to get solved this
> morning...
>
> I have two database tables (mysql). One contains information about
> images (filename, image description, directory path), the other contains
> two columns - one is the ID of the image and the other is an ID that
> represents an image category.
>
> The reason for doing this is so that I can have an image in multiple
> categories. Ie. An Image is a product image and also a promotional
> image (for example).
>
> Now I want to randomly select an image from my database such that it
> belongs in a set category. This isn't a problem and I have the code
> working fine. I am having trouble with the twist on this though. I
> want to be able to select an image based on it being in a certain
> category but also to be able to exclude that image if it is in a
> different category. That is, I want to select images in category 3 but
> only if they are not also in category 5 (for example).
>
> Can this be done in a single mysql query or am I going to have to link a
> series of mysql queries together with some php code to firstly get a set
> of images that are in one category (into an array for eg) and then go
> through and remove anything that's also in another category and then do
> a random selection from the remaining contents of the array?
>
> I'd like to think it can be done in a single mysql query and it would
> certainly be more elegant but I haven't been able to figure out a way
> and I'm starting to think I'll need to do it by manipulating arrays in
> php which would be far less elegant (although obviously still do-able).
>
> Any suggestions anyone? Or references to a tutorial/website somewhere
> that talks about doing this sort of thing would also be fine.
>
> Thanks
> Dave
>
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