tascam that won't work in this case for three reasons. The first is you are filtering from category_id when you must mean product_category.
Secondly your where statement is not correct. You are probably working on the lines of
which means find all records where the category_id is any one of those numbers.
Thirdly the request is to find records where a product_category contains 14, 11 AND 7 not or. You want to find those IDs that have all 3 numbers somewhere in the table.