how to repersent N:M in DBIx?

Pl refer to this link, it has my exact problem (but it only tells about SQL solution): http://stackoverflow.com/questions/11409869/mysql-nm-relationship-find-rows-with-several-specific-relations
I have three tables:1. products:-> prod-id, prod-name
2. tags:-> tag-id, tag-name
3. product_tags::-> prod-id, csv_tag_id
i read elsewhere on internet that this is not a good database/table design. so i am ready to change that too, but i could not think of any other way to represent this relationship. a given product could have multiple tags, but i have to find - at a given time - only those products which have 'ALL' of multiple given tags.
the SQL suggested on the page is:
SELECT a.*
FROM products a
INNER JOIN product_tags b ON a.product_id = b.product_id
WHERE b.tag_id IN (1,23,54)
GROUP BY a.product_id
HAVING COUNT(1) = 3thank you.Rajeev