[Solved] Complicated MySQL Query (Sets)

[eluser]mddd[/eluser]
If you need all tags to be linked, you could do something like this. The requested tag id's are 123 and 456 in this example.

Code:

SELECT product.* FROM product
JOIN product_tag tag1 ON tag1.product_id = product.id AND tag1.tag_id = 123
JOIN product_tag tag2 ON tag2.product_id = product.id AND tag2.tag_id = 456

So, you join the product able against the product_tag table several times. Each time on the condition that the tag matches.
This is easy to write in Active Record in CI, no matter how many tags were selected.