Question

这一点很有效：

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

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

您无法在更新语句中使用group by。您需要使用子选择进行分组。

这样的事情：

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

有人赞成连接操作的新式JOIN ... ON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

Answer 3

试试这个：

update 
    products, 
    (select 
        products_id, sum(attributes_stock) as sumAttr
     from products_attributes
     group by products_id) as a
set
    products.products_cuantity = a.sumAttr
where
    products.products_id = a.products_id

在多个表中使用sum（）结果的MYSQL更新

3 个答案: