SQL:添加两个求和字段并将求和值与另一个字段值进行比较

Question

好的，大家关于这个主题的最后一个问题(我希望)。

我需要做的是对两个不同表中的字段进行求和，将它们加在一起，然后检查这个总数是否大于该客户的信用额度。

我已将问题分解为更小的任务，以便我可以尝试提出整体解决方案。 (这些较小的代码对我来说工作正常，但是当组合到第三段代码中时，它们的总和不正确)。首先，我计算了第一个求和字段，如下所示:

 --summmed open invoices

 SELECT company,  sum(unit_price * invoice_qty) as open_invoices

 FROM 
  (SELECT arc.company, ard.unit_price, ard.invoice_qty, arc.credit_limit
   FROM iqms.arprepost_detail ard, iqms.arprepost arp, iqms.arcusto arc
   WHERE ard.arprepost_id = arp.ID
       AND arp.arcusto_id = arc.ID)

 GROUP BY company
 ORDER BY company;

这里的数字在求和时是正确的，我已经手动检查过。接下来我总结了我需要的其他字段，如下所示:

 --summed open orders

 SELECT company, (sum (unit_price * total_qty_ord)) as total_open_orders

 FROM 
   (SELECT arc.company, od.unit_price, od.total_qty_ord, arc.credit_limit   
    FROM iqms.arcusto arc, iqms.orders o, iqms.ord_detail od
    WHERE od.orders_id = o.ID
       AND o.arcusto_id = arc.ID
       AND (od.cumm_shipped < od.total_qty_ord  OR od.cumm_shipped IS NULL))

 GROUP BY company
 ORDER BY company;

这些数字在手动检查中再次正确显示。

我现在需要的是将这两个计算结果加在一起，并检查该数字是否大于该客户的“credit_limit”字段。我已经为此编写了代码，但数字超出了应有的范围(下面给出了此代码)。

 --summmed open invoices + open orders

  SELECT company, credit_limit, 
        round(sum(i_up * invoice_qty)) AS total_invoices, 
        round(sum (o_up * total_qty_ord)) AS total_orders,
        round(sum(i_up * invoice_qty) + sum (o_up * total_qty_ord)) as overall_total

 FROM 
   (SELECT arc.company, arc.credit_limit, ard.unit_price as i_up, ard.invoice_qty, od.unit_price as o_up, od.total_qty_ord 
    FROM iqms.arprepost_detail ard, iqms.arprepost arp, iqms.arcusto arc, iqms.orders o, iqms.ord_detail od
    WHERE 
       ard.arprepost_id = arp.ID      
       AND arp.arcusto_id = arc.ID
       AND od.orders_id = o.ID
       AND o.arcusto_id = arc.ID
       AND (od.cumm_shipped < od.total_qty_ord  OR od.cumm_shipped IS NULL)
   )

 GROUP BY company, credit_limit
 HAVING ((sum(i_up * invoice_qty)) + (sum (o_up * total_qty_ord)) > credit_limit)
 ORDER BY company;

我不知道我哪里错了。也许这是一个简单的修复，或者也许我的逻辑有问题。任何见解都将受到高度赞赏。非常感谢您一直以来的支持。

Answer 1

我的第一个观察是您应该使用 explicit joins instead of implicit joins ，隐式连接已经过时了 20 年

您无法像以前那样合并两个查询，因为它们来自不同的表，使用隐式联接这样做会导致交叉联接。我认为最简单的方法是为每个查询使用 2 个左连接:

SELECT  arc.Company,
        arc.Credit_Lime,
        COALESCE(Open_Orders, 0) AS Open_Orders,
        COALESCE(Open_Invoices, 0) AS Open_Invoices
        COALESCE(Open_Orders, 0) + COALESCE(Open_Invoices, 0) AS Total_Amount
FROM    iqms.arcusto arc
        LEFT JOIN
        (   SELECT  o.arcusto_ID
                    SUM(od.unit_price * od.total_qty_ord) AS Open_Orders
            FROM    iqms.orders o
                    INNER JOIN iqms.ord_detail od
                        ON od.orders_ID = o.ID
            WHERE   od.Cumm_Shipped < od.Total_qty_Ord
            OR      od.Cumm_Shipped IS NULL
            GROUP BY o.arcusto_ID
        ) openOrders
            ON openOrders.Arcusto_ID = arc.ID
        LEFT JOIN
        (   SELECT  arp.arcusto_id,
                    SUM(Unit_Price * Invoice_Quantity) AS Open_Invoices
            FROM    iqms.arprepost_detail ard
                    INNER JOIN iqms.arprepost arp
                        ON  ard.arprepost_id = arp.ID
            GROUP BY arp.arcusto_id
        ) OpenInvoices
            ON OpenInvoices.Arcusto_ID = arc.ID
WHERE   COALESCE(Open_Orders, 0) + COALESCE(Open_Invoices, 0) > arc.Credit_Limit;

您还可以将两个查询联合起来，如下所示:

SELECT  arc.Company,
        arc.Credit_Lime,
        SUM(COALESCE(Open_Orders, 0)) AS Open_Orders
FROM    iqms.arcusto arc
        LEFT JOIN
        (   SELECT  o.arcusto_ID
                    SUM(od.unit_price * od.total_qty_ord) AS Open_Orders
            FROM    iqms.orders o
                    INNER JOIN iqms.ord_detail od
                        ON od.orders_ID = o.ID
            WHERE   od.Cumm_Shipped < od.Total_qty_Ord
            OR      od.Cumm_Shipped IS NULL
            GROUP BY o.arcusto_ID
            UNION ALL
            SELECT  arp.arcusto_id,
                    SUM(Unit_Price * Invoice_Quantity) AS Open_Invoices
            FROM    iqms.arprepost_detail ard
                    INNER JOIN iqms.arprepost arp
                        ON  ard.arprepost_id = arp.ID
            GROUP BY arp.arcusto_id
        ) OpenInvoices
            ON OpenInvoices.Arcusto_ID = arc.ID
GROUP BY arc.Company, arc.Credit_Limit
HAVING  SUM(Open_Orders) > arc.Credit_Limit;

但我认为第一个在确定 Open_Orders 或 Open_Invoices 是否超出信用限额方面提供了更大的灵活性