更新子查询返回 EMPTY/NULL MYSQL

Question

我有这个数据库：

• 表 1 产品：id、name、total_sales

• 表2 Products_sales：id_product、id_user、price

我想使用此查询更新列“total_sales”

UPDATE products p SET total_sales = (SELECT SUM(price) AS totalPrice
FROM `products_sales` WHERE id_product = p.id GROUP BY id_product)

但是，如果一种产品没有任何销售，我会收到此错误：

#1048 - Column 'total_sales' cannot be null

当产品没有销售时，如何避免此错误？

也许使用后备值？

Answer 1

作为后备，您可以在COALESCE中使用零

UPDATE
    products AS p
        INNER JOIN (
        SELECT id_product, COALESCE(SUM(price), 0) AS totalPrice
        FROM `products_sales`
        GROUP BY id_product
    ) AS pSub ON p.id = pSub.id_product
SET p.total_sales = pSub.totalPrice;