将1个表中的3行联接到另一个表中的1行

Question

我需要创建一个记录集，该记录集将一个表的3行连接到另一表的1行。

目前我有：

   SELECT * 
     FROM tb_product_sub_cat 
LEFT JOIN tb_products ON tb_product_sub_cat.category_id = tb_products.product_subcategory 
    WHERE tb_product_sub_cat.category_name = %s 

我也需要：

tb_product_sub_cat.category_id = tb_products.product_subcategory2 AND
tb_product_sub_cat.category_id = tb_products.product_subcategory3

我需要查找所有/或所有产品类别中都包含“填充物”的所有产品。

Answer 1

SELECT * FROM tb_product_sub_cat 
INNER JOIN tb_products 
ON tb_product_sub_cat.category_id =   tb_products.product_subcategory2 
AND tb_product_sub_cat.category_id = tb_products.product_subcategory3 
AND   tb_product_sub_cat.category_id =  tb_products.product_subcategory  
WHERE tb_product_sub_cat.category_name = %s 

这是我对您的情况的解释。 让我知道这是否适合您或您需要详细说明。

编辑

SELECT * FROM tb_product_sub_cat 
LEFT JOIN tb_products 
ON tb_product_sub_cat.category_id =   tb_products.product_subcategory2 
AND tb_product_sub_cat.category_id = tb_products.product_subcategory3 
AND   tb_product_sub_cat.category_id =  tb_products.product_subcategory  
WHERE tb_product_sub_cat.category_name = %s

Answer 2

不清楚您想听什么，但这看起来像是UNION的工作：-

    SELECT * FROM tb_product_sub_cat LEFT JOIN tb_products ON tb_product_sub_cat.category_id = tb_products.product_subcategory WHERE tb_product_sub_cat.category_name = %s 
UNION
SELECT * FROM tb_product_sub_cat LEFT JOIN tb_products ON tb_product_sub_cat.category_id = tb_products.product_subcategory2 WHERE tb_product_sub_cat.category_name = %s
UNION
SELECT * FROM tb_product_sub_cat LEFT JOIN tb_products ON tb_product_sub_cat.category_id = tb_products.product_subcategory3 WHERE tb_product_sub_cat.category_name = %s

Answer 3

表别名将使您的生活更轻松：

   SELECT * 
     FROM tb_product_sub_cat t
LEFT JOIN tb_products tp ON t.category_id IN (tp.product_subcategory, tp.product_subcategory2, tp.product_subcategory3)
    WHERE t.category_name = %s