3-9 聚合管道

以链接的表为例,实现order,order_item表以order_id实现关联查询

1.联表查询

//order.js
const mongoose = require('./db');
const OrderSchema = new mongoose.Schema({
    order_id:String,
    status:String,
    amount:Number
})
module.exports = mongoose.model("Order",OrderSchema,"order");

//order_item.js
const mongoose = require('./db');
const OrderItemSchema = new mongoose.Schema({
    order_id:String,
    title:String,
    price:Number,
    num:Number
})
module.exports = mongoose.model('OrderItem',OrderItemSchema,'order_item');

//app.js
const OrderModel = require('./model/order');
OrderModel.aggregate([{
    $lookup:{
        from:'order_item',
        localField:"order_id",
        foreignField:"order_id",
        as:"items"
      }
}],(err,docs)=>{
    console.log(docs)
})

OrderModel.aggregate()是promise

const OrderModel = require('./model/order');
OrderModel.aggregate([{
    $lookup:{
        from:'order_item',
        localField:"order_id",
        foreignField:"order_id",
        as:"items"
      }
}]).then(data=>{
    console.log(data)
})

2.order_item表查询title为酸奶的order表的order_id,以及all_price

var orderToItem = OrderItemModel.aggregate([{
    $lookup:{
        from:'order',
        localField:'order_id',
        foreignField:'order_id',
        as:'infos'
    }
},{
    $match:{title:"酸奶"}
}])

3.mongoose获取ObjectId

{_id:mongoose.Types.ObjectId('xxxxx')}