Thanks! I will work with that. I need to get my head around JOIN ...
at the moment i am using this:

SELECT
activity.activity_id, activity_title, activity_photo,
activity_short_desc, activity_category.category_id,
activity_country.country_id
FROM
activity, activity_category, activity_country
WHERE
activity_category.category_id ='5' // or whatever
AND activity_country.country_id = '$country_id'
AND activity.activity_id = activity_country.activity_id
AND activity.activity_id = activity_category.activity_id

At least for the moment it is working. But I'm not sure it's the
correct (or most efficient) way to go about things, and I am having an
impossible time creating similar queries. Is the JOIN method more
efficient? Thanks again.

On Apr 22, 4:15 pm, "Rik Wasmus" <luiheidsgoe...@hotmail.com> wrote:
> On Tue, 22 Apr 2008 10:43:22 +0200, Captain Paralytic
>
>
>
> <paul_laut...@yahoo.com> wrote:
> > On 22 Apr, 05:03, cruiserweight <bayo...@yahoo.com> wrote:
> >> I am at the limits of my limited mysql knowledge. I have five tables:
> >> activity, country, category, activity_category, activity_country.
>
> >> activity is a table of holiday activities, for example "camping in
> >> yosemite" or "rock climbing in moab"; country is a list of countries
> >> (1=usa, 2=mexico, 3=canada, 4=brazil, 5=italy, etc); category is a
> >> list of activity types: camping, diving, rock climbing, cycling, etc.
> >> activity_category is two fields, activity_id and category_id;
> >> activity_country the same; activity_id and country_id.
>
> >> activities can have more than one country as well as more than one
> >> category (a hiking and cycling trip though italy and france, for
> >> example).
>
> >> What I am trying to select is activities by country by category, for
> >> example, cycling trips in italy. I assume my tables are set up
> >> correctly? I don't quite understand table joins, and i suspect that
> >> this might be the answer to my problem. if someone could help explain,
> >> or point me in the right direction to learn on my own, i would be
> >> forever grateful. thanks very much in advance for your time and help.
>
> > I don't see the need for the "activities" table.
> > country, category, country_category
> > would seem to serve the same purpose
>
> Unless as I suspect activities are an integral part of his data and goal
> to maintain. It's not the question wether or not a country has certain
> activities, but wether there are certain (scheduled?) activities in that
> country involving one of the categories. It could even be possible
> activities cross borders and as the OP indicated an activity has several
> categories.
>
> For readabilities sake I'd split it into multiple queries (possibly
> determenining category.id and country.id beforehand). However, it should
> be possible in one query, allthough it seems less efficient:
>
> SELECT
> act.id, act.name
> FROM countries cn
> JOIN activity_country acn
> ON acn.country_id = cn.id
> JOIN activities act
> ON act.id = acn.act_id
> JOIN activity_category ac
> ON ac.act_id = at.id
> JOIN categories cat
> ON cat.id = ac.cat_id
> AND cat.name LIKE 'cycling'
> WHERE cn.name LIKE 'Italy'
> GROUP BY act.id
>
> If you know the country.id & activity.id it becomes somewhat simpler:
>
> SELECT act.id, act.name
> FROM activity_country acn
> JOIN activities act
> ON act.id = acn.act_id
> JOIN activity_category ac
> ON ac.act_id = at.id
> AND ac.id = <activity.id>
> WHERE acn.country_id = <country.id>
> --
> Rik Wasmus