Question

我需要创建一个记录集，该记录集从另一个表的一行中的一个表中连接3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

我还需要：

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

我需要找到所有产品类别中包含“东西”的产品。

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

这是我对你的场景的解释。如果这对你有用或者你需要详细说明，请告诉我。

修改

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

不完全清楚你想听到什么，但这看起来像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

表别名会让您的生活更轻松：

   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

在另一个表中将1个表中的3行连接到1行

3 个答案: