Question

Something is wrong with my MySQL query below but I can’t find the problem. It’s not returning any errors but the query below should return 1 row, but it returns none.

The table ‘fws_product’ contains all products. The table ‘webits_product_has_kenmerken’ contains the product specifications.

SELECT fws_product.* 
FROM webits_product_has_kenmerken 
LEFT JOIN fws_product ON webits_product_has_kenmerken.product_id = fws_product.ID 
WHERE fws_product.CATID = 11 
AND ( 
(webits_product_has_kenmerken.kenmerk_id = 8 AND webits_product_has_kenmerken.kenmerk_value = 'Buddha to Buddha') 
AND
(webits_product_has_kenmerken.kenmerk_id = 19 AND webits_product_has_kenmerken.kenmerk_value = '10 mm')
)

Thanks in advance!

Answer 1

It looks a bit nasty, but the following should do as you have requested

SELECT
    p.*
FROM fws_product AS p

INNER JOIN webits_product_has_kenmerken AS ps8 
    ON ps8.product_id = p.ID
    AND ps8.kenmerk_id = 8
    AND ps8.kenmark_value = 'Buddha to Buddha'

INNER JOIN webits_product_has_kenmerken AS ps19 
    ON ps19.product_id = p.ID
    AND ps19.kenmerk_id = 19
    AND ps19.kenmark_value = '10 mm'

WHERE p.CATID = 11

This is another potential option which may do the job, but still feels very nasty

SELECT
    p.*
FROM fws_product AS p
INNER JOIN (
    SELECT 
        product_id,
        COUNT(*) AS numMatches
    FROM webits_product_has_kenmerken
    WHERE (kenmerk_id,kenmerk_value) IN (
            (8,'Buddha to Buddha'),
            (19,'10 mm')
        )
    GROUP BY product_id
    HAVING numMatches = 2
) AS ps
ON ps.product_id = p.ID

WHERE p.CATID = 11