我试图进行这样的查询:
$query= "SELECT a.virtuemart_category_id,
a.virtuemart_product_id,
b.product_name,
b.product_desc,
c.product_price,
d.virtuemart_media_id,
e.file_url
FROM wgny6_virtuemart_product_categories a
LEFT JOIN wgny6_virtuemart_products_en_gb b
ON a.virtuemart_product_id = b.virtuemart_product_id
LEFT JOIN wgny6_virtuemart_product_prices c
ON b.virtuemart_product_id = c.virtuemart_product_id
LEFT JOIN wgny6_virtuemart_product_medias d
ON b.virtuemart_product_id = d.virtuemart_product_id
LEFT JOIN wgny6_virtuemart_medias e
ON d.virtuemart_media_id = e.virtuemart_media_id
WHERE b.product_name IS NOT NULL";
但我希望只有当 a.virtuemart_category_id= $id 时才会发生这种情况。但我不知道如何添加该条件。