[英]How to select rows from another table if not enough rows in the first? With SQL
[英]SQL: How select rows and minus from another table
按产品对您的订单进行分组以获得产品的pc
列的sum
。
然后join
总和到你的product
表,减去订单从您的总和pc
-column在product
表。
SELECT
product.id_product,
(product.pc - ifnull(orders.amount, 0))
FROM
product
LEFT JOIN (
SELECT
id_product,
SUM(pc) AS amount
FROM
`Order`
GROUP BY
id_product
) AS orders ON orders.id_product = product.id_product
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.