Php 如何使用多个select查询优化UNION mysql查询？

我要求在产品详细信息页面中显示类似的产品，这样列出的产品应该以如下所示的分层方式匹配当前的产品属性

尺寸、颜色、类别、公司应与当前产品相匹配

尺寸、颜色、类别应与当前产品相匹配

尺寸、颜色应与当前产品相匹配

尺寸应与当前产品相匹配

我的sql查询如下所示：

(SELECT pd.product_id, pd.name, p.price 
        FROM mg_product_description pd 
            JOIN `mg_product` p ON p.product_id = pd.product_id 
        WHERE 
            pd.size_id = '33' AND 
            pd.color_id = '2' AND 
            pd.category_id = '3' AND 
            pd.company_id = '1'  AND 
            pd.product_id != '53'  AND 
            p.status = '1' 
            ORDER BY RAND() LIMIT 10 
    )
        UNION
    (SELECT pd.product_id, pd.name, p.price 
        FROM mg_product_description pd 
            JOIN `mg_product` p ON p.product_id = pd.product_id 
        WHERE 
            pd.size_id = '33' AND 
            pd.color_id = '2' AND 
            pd.category_id = '3'  AND 
            pd.product_id != '53'  AND 
            p.status = '1' 
            ORDER BY RAND() LIMIT 10 
    )
        UNION
    (SELECT pd.product_id, pd.name, p.price 
        FROM mg_product_description pd 
            JOIN `mg_product` p ON p.product_id = pd.product_id 
        WHERE 
            pd.size_id = '33' AND 
            pd.color_id = '2' AND 
            pd.product_id != '53'  AND 
            p.status = '1' 
            ORDER BY RAND() LIMIT 10 
    )
        UNION
    (SELECT pd.product_id, pd.name, p.price 
        FROM mg_product_description pd 
            JOIN `mg_product` p ON p.product_id = pd.product_id 
        WHERE 
            pd.size_id = '33' AND 
            pd.product_id != '53' AND 
            p.status = '1'
            ORDER BY RAND() LIMIT 10 
    )

53-当前产品id和状态表示可用

有没有办法优化上述查询

注意所需输出量：我们需要10种类似产品。如果存在4个符合条件1的产品，则需要按照随机顺序首先列出。同样，我们需要在下面列出符合其他条件的产品

提前谢谢

继续使用ORDER BY RAND（）（效率不高），那么一个非常基本的改进就是为每个子句添加优先级，将ORDER子句移到末尾，这样只需要一次

(SELECT pd.product_id, pd.name, p.price , 1 AS recpriority
        FROM mg_product_description pd 
            JOIN `mg_product` p ON p.product_id = pd.product_id 
        WHERE 
            pd.size_id = '33' AND 
            pd.color_id = '2' AND 
            pd.category_id = '3' AND 
            pd.company_id = '1'  AND 
            pd.product_id != '53'  AND 
            p.status = '1' 
    )
        UNION
    (SELECT pd.product_id, pd.name, p.price , 2 AS recpriority
        FROM mg_product_description pd 
            JOIN `mg_product` p ON p.product_id = pd.product_id 
        WHERE 
            pd.size_id = '33' AND 
            pd.color_id = '2' AND 
            pd.category_id = '3'  AND 
            pd.product_id != '53'  AND 
            p.status = '1' 
    )
        UNION
    (SELECT pd.product_id, pd.name, p.price , 3 AS recpriority
        FROM mg_product_description pd 
            JOIN `mg_product` p ON p.product_id = pd.product_id 
        WHERE 
            pd.size_id = '33' AND 
            pd.color_id = '2' AND 
            pd.product_id != '53'  AND 
            p.status = '1' 
    )
        UNION
    (SELECT pd.product_id, pd.name, p.price , 4 AS recpriority
        FROM mg_product_description pd 
            JOIN `mg_product` p ON p.product_id = pd.product_id 
        WHERE 
            pd.size_id = '33' AND 
            pd.product_id != '53' AND 
            p.status = '1'
    )
    ORDER BY recpriority, RAND() LIMIT 10 

这样做就不需要工会了：-

SELECT pd.product_id, 
    pd.name, 
    p.price , 
    CASE
        WHEN pd.color_id = '2' AND pd.category_id = '3' AND pd.company_id = '1'  THEN 1 
        WHEN pd.color_id = '2' AND pd.category_id = '3' THEN 2 
        WHEN pd.color_id = '2' THEN 3 
        ELSE 4 
    END AS recpriority
FROM mg_product_description pd 
JOIN `mg_product` p ON p.product_id = pd.product_id 
WHERE pd.size_id = '33' 
AND pd.product_id != '53' 
AND p.status = '1'
ORDER BY recpriority, RAND() 
LIMIT 10 

---

ORDER BY RAND（）通常比较慢，不过您需要提供解释输出。谢谢您的评论。我已经更新了这个问题。很抱歉不清楚，但我刚才说的“优化”是指上述查询的“提高性能”还是“降低复杂性”？两者都有。优先改善性能！！令人惊叹的！非常感谢：）！是否有其他方法可以选择随机行（…使用ORDER BY RAND（）（这是无效的）…是的。我使用了更有效的方法返回一行（基本上是在最小id和最大id之间获得一个随机值，然后选择该随机值上方的第一个id），但不确定在检索10时可以使用哪个方法。这篇文章可能对你决定一个好的随机方法很有用-