想知道是否有一种方法可以获得与出口日期相同的商品的库存案例列的总和？
更新了fiddle和一些相关数据：
https://www.db-fiddle.com/f/szc1ftj3zgec24gsyp6ad4/4
预期结果如下：

这是使用的查询

SELECT 
    st.product_code,
    st.date_of_export,
    st.best_before_date,
    st.stock_case,
    (
    SELECT 
            SUM(st2.stock_case)
        FROM
            stock_tracking AS st2
            WHERE
            st2.product_code IN ('MGN003')
        AND MONTH(st2.date_of_export) IN (07)
        AND YEAR(st2.date_of_export) IN (2018)
        AND st2.stock_case != 0
    ) AS total
    FROM
    stock_tracking st
WHERE
    product_code IN ('MGN003')
        AND MONTH(st.date_of_export) IN (07)
        AND YEAR(st.date_of_export) IN (2018)
        AND stock_case != 0

我的结果呢

希望有一个16，16，16，19等等，在另一个例子中，我使用了这样的子查询

SELECT 
    d.products_name,
    stock_case,
    st.date_of_export,
    st.best_before_date,
    st.product_code,
    (SELECT 
            SUM(st2.stock_case)
        FROM
            stock_tracking AS st2
        WHERE
            DATE(st2.date_of_export) = (SELECT 
                    DATE(tmp.last_update)
                FROM
                    (SELECT 
                        date_of_export AS last_update
                    FROM
                        stock_tracking
                    ORDER BY date_of_export DESC
                    LIMIT 1) AS tmp
                WHERE
                    product_code = 'MGN003')) AS total
FROM
    stock_tracking st
        LEFT JOIN
    products AS p ON p.products_model = st.product_code
        LEFT JOIN
    products_description AS d ON d.products_id = p.products_id
WHERE
    product_code = 'MGN003'
        AND d.language_id = 2
        AND DATE(st.date_of_export) = (SELECT 
            DATE(tmp.last_update)
        FROM
            (SELECT 
                date_of_export AS last_update
            FROM
                stock_tracking AS st
            ORDER BY date_of_export DESC
            LIMIT 1) AS tmp)

结果如下：