Sequelize：在模型 A 的子集上，对关联模型 B 的整数属性求和答案

【问题标题】：Sequelize: on a subset of model A, sum an integer-attribute of an associated model BSequelize：在模型 A 的子集上，对关联模型 B 的整数属性求和
【发布时间】：2016-12-01 18:51:40
【问题描述】：

我想这样做：

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;

结果在我的数据库中：

 sum 
-----
 151

(1 row)

我该怎么做？

我的 Sequelize 解决方案：

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})

经过数小时的研究，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

导致这条sql：

SELECT "orderArticles"."quantity", sum("quantity") AS "sum", "order"."id" AS "order.id", "order"."taxRate" AS "order.taxRate", "order"."shippingCosts" AS "order.shippingCosts", "order"."discount" AS "order.discount", "order"."paid" AS "order.paid", "order"."dispatched" 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 在 "orderArticles"."orderId" = "order"."id" 上加入 "orders" 作为 "order" AND "order"."paid" 不是 NULL WHERE "orderArticles"."discountTagId" = '4' GROUP BY "order"."id", "orderArticles"."quantity";

在同一个数据库上有这个结果：0 rows

如果你知道我做错了什么，请告诉我！谢谢你:)

【问题讨论】：

标签： sql join associations subset sequelize.js

【解决方案1】：

找到解决方案：

在 orderArticle 模型的范围定义中：

scopes: {
    paidOrders: {
        include: [{ 
            model: order, 
            where: { paid: {$ne: null}}, 
            attributes: [] // don't select additional colums!
        }]
    }
},
//...

和算法：

db.models.orderArticles
    .scope('paidOrders')
    .sum('quantity', {
        attributes: [], // don't select any further cols
        where: {discountTagId: 2}
    })

注意：在我的情况下，返回承诺就足够了。我使用 GraphQL 解析结果并将其发送给客户端。

【讨论】：