在多个表中使用sum()结果的MYSQL更新

Question

这个位工作得很好:

 SELECT products_id, sum(attributes_stock) 
 FROM products_attributes 
 GROUP BY products_id

这会将attributes_stock列中的所有字段组合在一起.

我遇到的问题是将此结果更新为另一个表中的另一列.

这就是我所拥有的:

 UPDATE products, products_attributes 
 SET products.products_quantity = sum(products_attributes.attributes_stock) GROUP BY products_attributes.products_id 
 WHERE products.products_id = products_attributes.products_id

任何建议都非常感谢.

Answer 1

您不能group by在更新语句中使用内部.您需要使用子选择来进行分组.

像这样的东西:

UPDATE products p,( SELECT products_id, sum(attributes_stock)  as mysum
                   FROM products_attributes GROUP BY products_id) as s

   SET p.products_quantity = s.mysum
  WHERE p.products_id = s.products_id

Answer 2

有些人喜欢JOIN ... ON连接操作的新式语法,而不是WHERE子句中的逗号运算符和连接谓词:

UPDATE products p
  JOIN ( SELECT q.products_id
              , SUM(q.attributes_stock) AS sum_attr
           FROM products_attributes q
          GROUP BY q.products_id
       ) r
    ON r.products_id = p.products_id
   SET p.products_quantity = r.sum_attr