MySQL 按产品 ID 分组，但不是具有序列号的产品

Question

有人可以帮助我如何为此进行有效的 mysql 查询吗？

我需要查询所有订购商品的总数量。

结合。

我需要查询所有收到的物品的总数量。

请注意，在我的“received_po_details”表中，有些产品在收到时有序列号，而有些则没有。这就是我遇到问题的地方，因为收到的总和由于序列号而增加了一倍。

表：received_po_details

i_rpoh_id   i_p_id  i_quantity_received s_product_serial
1           1       100 
1           2       100 
1           3       50  
1           4       25  
1           7       100 
1           8       50  
1           6       1                   XYZ1
1           6       1                   XYZ2
1           5       1                   ABC1
1           5       1                   ABC2

现在我有这两个需要组合的单独的 sql。 如果可能，我不想为此使用 Union 语句...

--获取订购的总数量

SELECT
    products.i_id AS 'ID',
    products.s_name AS 'Name',
    COALESCE(SUM(purchase_order_details.i_quantity_ordered),0) AS 'Total Quantity Ordered'
FROM
    products
LEFT JOIN
    purchase_order_details
    ON
    products.i_id = purchase_order_details.i_p_id
GROUP BY
    products.i_id   

-- to get the Total Quantity Received
SELECT
    products.i_id AS 'ID',
    products.s_name AS 'Name',
    COALESCE(SUM(received_po_details.i_quantity_received),0) AS 'Total Quantity Received'
FROM
    products
LEFT JOIN
    received_po_details
    ON
    products.i_id = received_po_details.i_p_id
GROUP BY
    products.i_id

Answer 1

您可以通过创建派生表或每种类型的总和来组合这些查询（在下面的查询中，它们被命名为 t1 和 t2）并将派生表连接到主产品表。

SELECT
    p.i_id AS 'ID',
    p.s_name AS 'Name',
    COALESCE(t1.total,0) 'Total Quantity Ordered',
    COALESCE(t2.total,0) 'Total Quantity Received'
FROM products p
LEFT JOIN (
    SELECT 
        pod.i_p_id,
        SUM(pod.i_quantity_ordered) total
    FROM purchase_order_details pod
    GROUP BY pod.i_p_id
) t1 ON t1.i_p_id = p.i_id
LEFT JOIN (
    SELECT 
        rpd.i_p_id,
        SUM(rpd.i_quantity_received) total
    FROM received_po_details rpd
    GROUP BY rpd.i_p_id
) t2 ON p.i_id = t2.i_p_id