Sequelize：在模型A的子集上，求和关联模型B的整数属性

I want to do this:

select sum("quantity") as "sum"
from "orderArticles" 
inner join "orders" 
on "orderArticles"."orderId"="orders"."id" 
and "orderArticles"."discountTagId" = 2
and "orders"."paid" is not null;

这导致我的数据库：

sum 
-----
 151

(1 row)

我该怎么做？

My Sequelize solution:

模型定义：

const order = Conn.define('orders', {
        id: {
            type: Sequelize.BIGINT,
            autoIncrement: true,
            primaryKey: true
        },
        // ...
        paid: {
            type: Sequelize.DATE,
            defaultValue: null
        },
        // ...
    },
// ...
})

const orderArticle = Conn.define('orderArticles', 
    {
        id: {
            type: Sequelize.BIGINT,
            autoIncrement: true,
            primaryKey: true
        },

        // ...

        quantity: {
            type: Sequelize.INTEGER,
            defaultValue: 1
        }
    },
    {
        scopes: {
            paidOrders: {
                include: [
                   { model: order, where: { paid: {$ne: null}} }
               ]
            }
        },
// ...
})

协会：

orderArticle.belongsTo(order)
order.hasMany(orderArticle, {onDelete: 'cascade', hooks: true})

经过几个小时的研究，我想出了这个：

db.models.orderArticles
 .scope('paidOrders') // select only orders with paid: {$ne: null}
 .sum('quantity', { // sum up all resulting quantities
    attributes: ['quantity'], // select only the orderArticles.quantity col
    where: {discountTagId: 2}, // where orderArticles.discountTagId = 2
    group: ['"order"."id"', '"orderArticles"."quantity"'] // don't know why, but Sequelize told me to
 })
.then(sum => sum) // return the sum

导致这个SQL：

SELECT“orderArticles” . “quantity”，sum（“quantity”）AS“sum”，“order” . “id”AS“order.id”，“order” . “taxRate”AS“order.taxRate”，“订单“ . ”shippingCosts“AS”order.shippingCosts“，”订单“ . ”折扣“AS”order.discount“，”订单“ . ”支付“AS”order.paid“，”订单“ . ”发送“AS” order.dispatched“，”order“ . ”payday“AS”order.payday“，”order“ . ”billNr“AS”order.billNr“，”order“ . ”createdAt“AS”order.createdAt“，”order“ . “updatedAt”AS“order.updatedAt”，“order” . “orderCustomerId”AS“order.orderCustomerId”，“order” . “billCustomerId”AS“order.billCustomerId”FROM“orderArticles”AS“orderArticles”INNER JOIN“命令“AS”订单“ON”orderArticles“ . ”orderId“=”order“ . ”id“AND”order“ . ”paid“IS NOT NULL WHERE”orderArticles“ . ”discountTagId“='4'GROUP BY”order“ . “id”，“orderArticles” . “数量”;

在同一数据库中有此结果： 0 rows

如果你知道我的错误，请告诉我！谢谢 ：）