SELECT p.* FROM products as p
JOIN product_filter as pf ON p.id=pf.product_id
WHERE pf.filter_id='1' AND pf.filter_id='2'
SELECT
p.*
FROM
products as p
WHERE
EXISTS (
SELECT 1 FROM product_filter pf WHERE pf.filter_id = 1 AND pf.product_id = p.id
)
AND EXISTS (
SELECT 1 FROM product_filter pf WHERE pf.filter_id = 2 AND pf.product_id = p.id
);