mongodb aggregation聚合管道 $lookup结合$match实现筛选

很多老前辈说mongodb没法实现关联查询。最新的mongodb有方法了

Mongodb Mongoose aggregation 视频教程： https://pan.baidu.com/s/1Dva3FBLYILWSPubHy8kOFA

mongodb aggregation文档地址： https://docs.mongodb.com/v3.2/reference/operator/aggregation/lookup/index.html

mongodb aggregation聚合管道 $lookup结合$match实现筛选

db.orders.aggregate([
   {
      $unwind: "$specs"
   },
   {
      $lookup:
         {
            from: "inventory",
            localField: "specs",
            foreignField: "size",
            as: "inventory_docs"
        }
   },
   {
      $match: { "inventory_docs": { $ne: [] } }
   }
])

phonegap100 1楼•4 年前作者

如果要筛选 inventory_docs中的字段的话就按照上面的写法

返回指定字段：

db.order.aggregate([
    {
      $lookup:
        {
          from: "order_item",
          localField: "order_id",
          foreignField: "order_id",
          as: "items"
        }
   },
 {
	$match:{"all_price":{$gte:90}}
 },{
    $project:{order_id:1,uid:1,trade_no:1,all_price:1,all_num:1,cate:{ items:1，price:1}}
    
  }

])