MongoDB聚合以对具有相似ID的产品价格求和
您需要使用$group对具有指定_id表达式的文档进行分组。首先让我们创建一个包含文档的集合-
> db.aggreagateDemo.insertOne({"Product_Id":1,"ProductPrice":50}); { "acknowledged" : true, "insertedId" : ObjectId("5e06d3c025ddae1f53b621d9") } > db.aggreagateDemo.insertOne({"Product_Id":2,"ProductPrice":100}); { "acknowledged" : true, "insertedId" : ObjectId("5e06d3c625ddae1f53b621da") } > db.aggreagateDemo.insertOne({"Product_Id":2,"ProductPrice":500}); { "acknowledged" : true, "insertedId" : ObjectId("5e06d3cb25ddae1f53b621db") } > db.aggreagateDemo.insertOne({"Product_Id":1,"ProductPrice":150}); { "acknowledged" : true, "insertedId" : ObjectId("5e06d3d125ddae1f53b621dc") }
以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.aggreagateDemo.find().pretty();
这将产生以下输出-
{ "_id" : ObjectId("5e06d3c025ddae1f53b621d9"), "Product_Id" : 1, "ProductPrice" : 50 } { "_id" : ObjectId("5e06d3c625ddae1f53b621da"), "Product_Id" : 2, "ProductPrice" : 100 } { "_id" : ObjectId("5e06d3cb25ddae1f53b621db"), "Product_Id" : 2, "ProductPrice" : 500 } { "_id" : ObjectId("5e06d3d125ddae1f53b621dc"), "Product_Id" : 1, "ProductPrice" : 150 }
这是执行聚合和ID分组的查询-
> db.aggreagateDemo.aggregate([ ... { ... $group: { ... _id: "$Product_Id", ... TotalValue:{$sum: "$ProductPrice"} ... } ... } ... ] ... );
这将产生以下输出-
{ "_id" : 2, "TotalValue" : 600 } { "_id" : 1, "TotalValue" : 200 }