How to get products without tag?

by

I’m going to answer my own question:

SELECT ID FROM wpyw_posts 
WHERE ID NOT IN (
    SELECT wpyw_term_relationships.object_id 
    FROM wpyw_term_relationships 
        INNER JOIN wpyw_term_taxonomy ON wpyw_term_taxonomy.term_id = wpyw_term_relationships.term_taxonomy_id 
    WHERE wpyw_term_taxonomy.taxonomy = 'product_tag'
) AND wpyw_posts.post_type="product"