MYSQL GROUP BY子句添加非GROUP BY列

Question

我在MySQL中有一个表，我想按操作分组。这是我的桌子

预期结果应该是按bag_no分组的价格总和，但product_id应该是mainproduct ='Y'。所以结果应该是这样

我可以执行以下操作

SELECT bag_no, sum(price) AS total_price 
FROM myTable
GROUP BY bag_no

但是，这不允许我在我也想要的表中添加product_id。我们该怎么做？

Answer 1

执行此操作的一种规范方法涉及加入子查询以查找总和：

SELECT
    t1.bag_no,
    t1.product_id,
    t2.total_price
FROM myTable t1
INNER JOIN
(
    SELECT bag_no, SUM(price) AS total_price
    FROM myTable
    GROUP BY bag_no
) t2
    ON t1.bag_no = t2.bag_no
WHERE
    t1.mainproduct = 'Y';

使用支持分析功能的MySQL 8+，我们可以稍微简化上述查询：

WITH cte AS (
    SELECT
        t1.bag_no,
        t1.product_id,
        SUM(price) OVER (PARTITION BY t1.bag_no) total_price,
        t1.mainproduct
    FROM myTable t1
)

SELECT bag_no, product_id, total_price
FROM cte
WHERE mainproduct = 'Y';