多对多的前5位关系

如何解决多对多的前5位关系

我的项目中有两个模型。

1. 订单
2. 产品
3. OrderProducts（至）（具有数量列）

我需要在一定时期内确认订单的5个购买量最大的产品

OrderProducts.init({
    order_id: DataTypes.INTEGER(4),product_id: DataTypes.INTEGER(4),qtd: DataTypes.INTEGER(4),price: DataTypes.DECIMAL(15,2),})

Orders.init({
    order_id: {
        type: DataTypes.INTEGER(4),primaryKey: true,autoIncrement: true,allowNull: false,},client_id: DataTypes.INTEGER(4),amount: DataTypes.DECIMAL(15,status: {
        type: DataTypes.ENUM([
            'PENDING','CONFIRMED','PROGRESS','CANCELED',]),defaultValue: 'PENDING',})

Products.init({
    product_id: {
        type: DataTypes.INTEGER(4),title: DataTypes.STRING(256),description: DataTypes.TEXT,})

Orders.belongsToMany(Products,{foreignKey: 'order_id',through: OrderProducts,as: 'products'})
Products.belongsToMany(Orders,{foreignKey: 'product_id',through: OrderProducts})

一种解决方案是通过...搜索表

解决方法

我以某种方式假设qtd是“数量”字段。如果没有，那么每个订单只能有每种产品类型之一，而不是尝试切换到COUNT()函数。我还假设您在“订单”表上有一个购买日期，您自然会称其为purchaseDate。

const queryStartDate = moment().subtract(1,'months').startOf('day');
const queryEndDate = moment().endOf('day');
Products.findAll({
  offset: 0,limit: 5,attributes: ['product_id','title',[sequelize.literal(`(
      SELECT SUM(op.qty)
      FROM OrderProducts AS op
      INNER JOIN Orders o ON o.order_id = op.order_id
      WHERE 
        op.product_id = Product.product_id
        AND o.purchaseDate >= $startDate
        AND o.purchaseDate <= $endDate
        AND o.status = 'CONFIRMED'
      )`,{
        bind: {
          startDate: queryStartDate,endDate: queryEndDate,},}),'summedQty']
  ],order: [[sequelize.literal('summedQty'),'DESC']]
});
// Note: 
//   - I'm assuming [OrderProducts] and [Orders] are the names of the actual SQL tables.
//   - In contrast,the `Product.product_id` reference is to whatever Sequelize renders the Products table's alias as,in the SQL query.  It'll be a reference to the parent of the sub-query.  This may need tweaking but it should be good-to-go.
//   - Were I you,I would put those statuses in a Look-up-Table.  Enums are great in applications but strings/varchars are costly in databases.
//   - I can't remember if the `Sequelize.literal()` function takes a `bind` attribute,like the `Sequelize.query()` function does.  If not,you'll have to use string interpolation and format-out the dates.

参考：

1. Ordering by an aggregate (SUM or COUNT) function.
2. Pagination.
3. Binding syntax for the Query() function.