Select rows with multiple tags… is there a better way?

Question

I am attempting to do a tag system for selecting products from a database. I have read that the best way to achieve this is via a many-to-many relationship as using LIKE \'%tag%

Answer 1

No need to do multiple joins. If you need to match all tags, you can use an IN clause with a subquery like this:

select p.sku, p.name, p.path 
from shop_products p
where p.sku in (
    select pc.product_sku 
    from shop_products_categories pc 
    inner join shop_categories c on pc.category_id = c.id
    where c.path in ('flowers', 'romance')
    group by pc.product_sku
    having count(distinct c.path) = 2
)

Note that you will need to adjust the number 2 to be the number of unique tags you are matching on. Beware in case this is user-entered data and they enter the same tag twice.