It looks like if you are passing in the user and catalogue id's then the supplier doesn't matter.
If you required the supplier information in the result, that would be a different matter.
It feels like you shouldn't be involving the user in this query at all as you seem to be looking for the images in a catalogue that are owned by a particular supplier.
If that is the case, then I would drop the requirement for the user id in the query and use the supplier id instead.
I am assuming that the user would have done the following to get to the point where they would be initiating this query:
- login - obviously :)
- click on 'list suppliers'
- click on a supplier
- click on a catalog
Either way you are going to have to do a lot of INNER JOIN's. For instance the query to retrieve the list of suppliers for a given user would be something like
SELECT
s.supplier_id,
s.Supplier_name
FROM
supplier s
INNER JOIN
user u
INNER JOIN
user2supplier u2s
ON
u.user_id = u2s.user_id
ON
u2s.supplier_id = s.supplier_id
WHERE
u.user_id = 3 -- for example...
(now, I haven't tested the SQL, but I think that is right...)
Let me know if I'm on the right track - if I have helped, I'd be happy to help some more if I can