使用多个连接时，Mysql sum 查询返回错误结果

我的查询返回了 2 个子表中 2 列的错误总和，我在 google 上进行了搜索，也查看了 stackoverflow 上的建议，但它们从未起作用。

   si_invoices
   -----------------------------
   id, date
   1, 2014-05-07


   si_invoice_items
   -----------------------------
   id, invoice_id, date , total
   1, 100, 2014-05-07, 200
   2, 100, 2014-05-07, 200

   si_payment
   -----------------------------
   id, ac_inv_id, date , payment
   1, 100, 2014-05-07, 100
   2, 100, 2014-05-07, 200

   SELECT  SI.*,SUM(SII.total) as total,SUM(SIP.payment) as payment FROM 
        (SELECT * FROM si_invoices GROUP BY si_invoices.id) AS SI
     LEFT JOIN si_invoice_items SII ON SII.invoice_id = SI.id
     LEFT JOIN si_payment SIP ON SIP.ac_inv_id = SII.invoice_id
   GROUP BY SI.id

它应该为 sql 中的字段“total”返回 400 总和，但它返回 800，与“ payment”相同。您能指出我的查询中有什么错误吗？请帮忙，不胜感激。

谢谢 多发性硬化症

直接使用总计，因为您的联接可能会创建更多您想要的组合行。

请尝试以下操作：

SELECT id, MAX(Total) as FinalTotal ,MAX(Payment) as FinalPayment
FROM si_invoices a 
    left join 
    (select invoice_id, sum(total) as Total from si_invoice_items group by invoice_id) b 
    on a.id = b.invoice_id
    left join
    (select ac_inv_id, sum(payment) as Payment from si_payment group by ac_inv_id) c 
    on c.ac_inv_id = a.id 
group by id

或者如果 id 是唯一的：

    SELECT *
FROM si_invoices a 
    left join 
    (select invoice_id, sum(total) as Total from si_invoice_items group by invoice_id) b 
    on a.id = b.invoice_id
    left join
    (select ac_inv_id, sum(payment) as Payment from si_payment group by ac_inv_id) c 
    on c.ac_inv_id = a.id