从两个表中求和，并与第三个表中的值进行比较

Question

我试图做一些我认为非常简单的事情，但无法在SQL语句中弄明白。 该表

1. 发票（列 - GrossAmount）

2. 收据（列 - ReceiptValue，有可能是一个收据或没有收据的话）

3. 信用票据（列 - GrossCredit，可能有信用票据或没有）

我想显示总未清发票，即显示所有发票其中Invoices.GrossAmount > (sum(Receipt.ReceiptValue) + sum(CreditNotes.GrossCredit))。

查询需要显示所有未完全支付或未支付的发票。

InvoiceId在所有表中与外键相同。

使用的MS SQL Server 2014

Answer 1

你需要总结每个表单独（按发票分组），然后按[左]连接的结果：

SELECT i.InvoiceId 
FROM invoices i 
LEFT JOIN (SELECT InvoiceId, SUM(ReceiptValue) AS sum_receipt 
      FROM  receipts 
      GROUP BY InvoiceId) r ON i.InvoiceId = r.InvoiceId 
LEFT JOIN (SELECT InvoiceId, SUM(GrossCredit) AS sum_credit 
      FROM  credit 
      GROUP BY InvoiceId) g ON i.InvoiceId = g.InvoiceId 
WHERE  i.GrossAmount > COALESCE(sum_receipt, 0) + COALESCE(sum_credit, 0) 

Answer 2

我想你想是这样的：

select i.*, 
     coalesce(r.sumrv, 0) as receiptValue, 
     coalesce(c.sumgc, 0) as grossCredits 
from invoices i left join 
    (select invoiceId, sum(receiptvalue) as sumrv 
     from receipts 
     group by invoiceId 
    ) r 
    on i.invoiceId = r.invoiceId left join 
    (select invoiceId, sum(grosscredit) as sumgc 
     from credits c 
     group by invoiceId 
    ) c 
    on i.invoiceId = c.invoiceId 
where i.GrossAmount > coalesce(r.sumrv, 0) + coalesce(c.sumgc, 0); 

三个重要的事情：

• 使用left join这样你就不会没有下降发票匹配一个或两个表中的记录。
• 使用coalesce()所以NULL值被视为0。
• 在加入表格之前，请执行汇总。