sql - 多表发票SUM比较

Question

假设我在 Rails 应用中有 3 个表:

发票

id  | customer_id  | employee_id  | notes
---------------------------------------------------------------
1   | 1            | 5            | An order with 2 items.
2   | 12           | 5            | An order with 1 item.
3   | 17           | 12           | An empty order.
4   | 17           | 12           | A brand new order.

invoice_items

id  | invoice_id  | price  | name
---------------------------------------------------------
1   | 1           | 5.35   | widget
2   | 1           | 7.25   | thingy
3   | 2           | 1.25   | smaller thingy
4   | 2           | 1.25   | another smaller thingy

invoice_payments

id  | invoice_id  | amount  | method      | notes
---------------------------------------------------------
1   | 1           | 4.85    | credit card | Not enough 
2   | 1           | 1.25    | credit card | Still not enough
3   | 2           | 1.25    | check       | Paid in full

这代表4个订单:

第一个有 2 个项目，总共 12.60。它有两次付款，总付款金额为 6.10。此订单已部分支付。

第二个只有一个项目和一个付款，两者合计 1.25。此订单已全额支付。

第三个订单没有商品或付款。这对我们很重要，有时我们会使用这种情况。它也被视为全额支付。

最终订单再次有一件商品，总共 1.25，但尚未付款。

现在我需要一个查询:

显示所有尚未全额付款的订单；也就是说，所有订单使得项目的总和大于付款的总和。

我可以在纯 sql 中做到这一点:

SELECT      invoices.*,
            invoice_payment_amounts.amount_paid AS amount_paid,
            invoice_item_amounts.total_amount AS total_amount
FROM        invoices
LEFT JOIN   (
                SELECT      invoices.id AS invoice_id,
                            COALESCE(SUM(invoice_payments.amount), 0) AS amount_paid
                FROM        invoices
                LEFT JOIN   invoice_payments
                ON          invoices.id = invoice_payments.invoice_id
                GROUP BY    invoices.id
            ) AS invoice_payment_amounts
ON          invoices.id = invoice_payment_amounts.invoice_id
LEFT JOIN   (
                SELECT      invoices.id AS invoice_id,
                            COALESCE(SUM(invoice_items.item_price), 0) AS total_amount
                FROM        invoices
                LEFT JOIN   invoice_items
                ON          invoices.id = invoice_items.invoice_id
                GROUP BY    invoices.id
            ) AS invoice_item_amounts
ON          invoices.id = invoice_item_amounts.invoice_id
WHERE       amount_paid < total_amount

但是......现在我需要把它放到 rails 中(可能作为一个范围)。我可以使用 find_by_sql，但它会返回一个数组，而不是一个 ActiveRecord::Relation，这不是我需要的，因为我想将它与其他范围链接(例如，有一个过期范围，它使用这个)， 等等。

所以原始 SQL 可能不是去这里的正确方法......但什么是？我无法在 activerecord 的查询语言中执行此操作。

到目前为止我得到的最接近的是这个:

Invoice.select('invoices.*, SUM(invoice_items.price) AS total, SUM(invoice_payments.amount) AS amount_paid').
  joins(:invoice_payments, :invoice_items).
  group('invoices.id').
  where('amount_paid < total')

但这失败了，因为在像 #1 这样的订单上，多次付款，它错误地将订单价格加倍(由于多次连接)，显示它仍未付款。我在 SQL 中遇到了同样的问题，这就是为什么我按照我的方式构建它。

这里有什么想法吗？

Answer 1

您可以使用 group by 获取结果和 having MySQL的子句为:

纯 MySQL 查询:

  SELECT `invoices`.* FROM `invoices` 
  INNER JOIN `invoice_items` ON 
    `invoice_items`.`invoice_id` = `invoices`.`id` 
  INNER JOIN `invoice_payments` ON 
    `invoice_payments`.`invoice_id` = `invoices`.`id` 
  GROUP BY invoices.id 
    HAVING sum(invoice_items.price) < sum(invoice_payments.amount) 

ActiveRecord 查询:

Invoice.joins(:invoice_items, :invoice_payments).group("invoices.id").having("sum(invoice_items.price) < sum(:invoice_payments.amount)")