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MongoDB aggregation to sum individual properties on an object in an array across documents
For this, use aggregate() in MongoDB. Let us first create a collection with documents −
> db.demo131.insertOne( ... { ... "_id": 101, ... "Details": [ ... { ... "PlayerScore": 500, ... "PlayerName": "Chris" ... }, ... { ... "PlayerScore": 400, ... "PlayerName": "David" ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" : 101 } > db.demo131.insertOne( ... { ... "_id": 102, ... "Details": [ ... { ... "PlayerScore": 600, ... "PlayerName": "Chris" ... }, ... { ... "PlayerScore": 200, ... "PlayerName": "David" ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" : 102 }
Display all documents from a collection with the help of find() method −
> db.demo131.find();
This will produce the following output −
{ "_id" : 101, "Details" : [ { "PlayerScore" : 500, "PlayerName" : "Chris" }, { "PlayerScore" : 400, "PlayerName" : "David" } ] } { "_id" : 102, "Details" : [ { "PlayerScore" : 600, "PlayerName" : "Chris" }, { "PlayerScore" : 200, "PlayerName" : "David" } ] }
Following is the query to sum individual properties on an object in an array −
> db.demo131.aggregate([ ... { $unwind: "$Details" }, ... { ... $group: { ... _id:"$Details.PlayerName", ... Value:{$sum:"$Details.PlayerScore"} ... } ... }, ... { ... $group: { ... _id: 0, ... Details:{ $push: {Details:"$_id",Value:"$Value"}} ... } ... }, ... { ... $project:{Details:1,_id:0} ... } ])
This will produce the following output −
{ "Details" : [ { "Details" : "David", "Value" : 600 }, { "Details" : "Chris", "Value" : 1100 } ] }
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