php - 更改 mysql 查询以始终返回结果

Question

我有一个查询，它检查与所显示的产品相关(相似)的信息，如果有的话，它会显示它们。如果没有任何相关(相似)产品来显示其他产品，如何更改它。这是查询:

select p.id,bg_product_name,unique_name,product_price,
promo_price, promo_end_date, available_qty,model,ptc.category_id, free_delivery, free_option
from products p, related_products rp, products_to_categories ptc where
 rp.product_id="10284" and rp.related_id=p.id and p.id=ptc.product_id and
 p.available_qty > 0 AND p.active="1" group by p.id limit 5

感谢您的帮助和建议!

Answer 1

试试这个

SELECT 
    p.id,bg_product_name,unique_name,product_price, promo_price, promo_end_date, 
    available_qty,model,ptc.category_id, free_delivery, free_option
FROM 
    products p
    LEFT OUTER JOIN products_to_categories ptc ON p.id=ptc.product_id
    LEFT OUTER JOIN related_products rp ON rp.related_id=p.id AND rp.product_id="10284"

WHERE
    p.available_qty > 0 AND p.active="1" 
GROUP BY p.id LIMIT 5