获取每个类别的产品销售总量的有效方法

Question

我有如下问题。我需要获取每个类别的产品销售总量。一种产品可以属于多个类别。一个类别还可以在一个类别中包含多个产品。我有以下方案：

//Categories scheme
{
  name: {
        type: String,
        required: [true, "The Category name is required"],
        unique: true,
    }}

 //Products
{
  name: {
        type: String,
        required: [true, "The prodcut name is required"],
        unique: true,
    }
    price: {
        type: mongoose.Types.Decimal128,
        default: "0.0",
    },
 }

 //Products Categories scheme
{ 
    product: {
        type: Schema.Types.ObjectId, ref: "Products",
    },
    category: {
        type: Schema.Types.ObjectId, ref: "Categories",
    },
 }
 //Orders model scheme
{ 
    product: {
        type: Schema.Types.ObjectId, ref: "Products",
    },
    price: {
        type: mongoose.Types.Decimal128,
        default: "0.0",
    },
    quantity: {
        type: Number,
        default: 0,
    }
 }

我有和上面一样的方案。我尝试按如下方式创建查询，但它只需要一个产品。

OrdersModel.aggregate(
        [
            { $lookup: { from: 'products', localField: 'product', foreignField: '_id', as: 'p' } },
            { $lookup: { from: 'prodcutcategories', localField: 'p._id', foreignField: 'product', as: 'pc' } },
            { $lookup: { from: 'categories', localField: 'pc.category', foreignField: '_id', as: 'cat' } },
            {
                $group:
                {
                    _id: "$cat.name", 
                }
            },
        ]
    )

此查询有效但生成了一个产品，如下所示：

{
"status": "Success",
"data": [
    {
        "_id": [
            "A category",
            "A product"
        ]
    }
 ]
}

但我需要这样:

{
"status": "Success",
"data": [
    {
        "category": "Category name 1",
        "totalPrice": 10000,
        "qty": 10000,
        "mostSoldProduct": "Product name",
        ...
    },
    {
        "category": "Category name 2",
        "totalPrice": 10000,
        "qty": 10000,
        "mostSoldProduct": "Product name",
        ...
    }
 ]
}

我应该得到与上面相同的结果。但是我说我在进行查询时错了吗？我在 MSSQL 中创建了一个类似于以下的查询。

select cat.name sum(o.price) from order o 
inner join products p on p.id=o.productid
inner join products_categories pc on p.id=pc.productid
inner join catrgories cat on cat.id=pc.category_id
group by cat.name

有哪些方法可以解决我的问题？我在 Google 上搜索了很多，但在 MongoDB 上找不到解决方案。感谢您的回答！

Answer 1

在管道阶段之后添加以下阶段，

$unwind解构cat数组生成对象
$unwind 解构 p 数组以创建对象
$group 按类别名称和计数所需的统计信息

  { $unwind: "$cat" },
  { $unwind: "$p" },
  {
    $group: {
      _id: "$cat.name",
      totalPrice: { $sum: "$price" },
      qty: { $sum: "$quantity" },
      totalSold: { $sum: 1 }
    }
  }

Playground

You really need to change your schema to modern schema, this structure is not good for mongo database.

获取每个类别的产品销售总量的有效方法

Efficient way to get the total amount of products sold by each category

lookup

group-by

mongodb

nosql

aggregation-framework