基于条件比较两个子表的聚合返回记录

Question

我有一个包含许多付款和许多发票行项目的发票表。发票记录的总和是通过发票行项目（数量 * 价格）得出的。

我正在尝试创建一个查询，该查询将返回未结余额的发票。

SELECT inv.id, MAX(inv.invoice_total) as "InvoiceTotal", SUM(pt.amount) AS "TotalPayments" FROM (
  SELECT 
        i.id,
        SUM( ili.price * ili.quantity ) as "invoice_total"
     FROM
        invoices i
        JOIN invoice_line_items ili
          on i.id = ili.invoice_id
  GROUP BY i.id
  ) inv
LEFT JOIN payment_transactions pt
ON pt.invoice_id = inv.id
GROUP BY inv.id
ORDER BY inv.id DESC

最后一点，我想，是添加 HAVING，它只返回 Total Payments 小于 Invoice Total 的记录，但它不起作用。

我怎样才能做到这一点？有比我更简单的方法吗？

Answer 1

这应该可行：

SELECT inv.id, MAX(inv.invoice_total) as InvoiceTotal, SUM(pt.amount) AS "TotalPayments"
FROM (SELECT i.id, SUM( ili.price * ili.quantity ) as invoice_total
      FROM invoices i JOIN 
           invoice_line_items ili
           ON i.id = ili.invoice_id
      GROUP BY i.id
     ) inv LEFT JOIN
     payment_transactions pt
     ON pt.invoice_id = inv.id
GROUP BY inv.id
HAVING COALESCE(SUM(pt.amount), 0) < MAX(inv.invoice_total)
ORDER BY inv.id DESC;