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Find maximum score for duplicate Name values in MongoDB?
To find maximum score, use GROUP() to group documents in a collection. Let us create a collection with documents −
> db.demo114.insertOne({"Score":60,"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e2efc57d8f64a552dae6354") } > db.demo114.insertOne({"Score":87,"Nam+e":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e2efc5ad8f64a552dae6355") } > db.demo114.insertOne({"Score":45,"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e2efc5dd8f64a552dae6356") } > db.demo114.insertOne({"Score":67,"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e2efc68d8f64a552dae6357") } > db.demo114.insertOne({"Score":38,"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e2efc74d8f64a552dae6358") }
Display all documents from a collection with the help of find() method −
> db.demo114.find();
This will produce the following output −
{ "_id" : ObjectId("5e2efc57d8f64a552dae6354"), "Score" : 60, "Name" : "Chris" } { "_id" : ObjectId("5e2efc5ad8f64a552dae6355"), "Score" : 87, "Name" : "Chris" } { "_id" : ObjectId("5e2efc5dd8f64a552dae6356"), "Score" : 45, "Name" : "David" } { "_id" : ObjectId("5e2efc68d8f64a552dae6357"), "Score" : 67, "Name" : "Chris" } { "_id" : ObjectId("5e2efc74d8f64a552dae6358"), "Score" : 38, "Name" : "David" }
Following is the query to find maximum. This calculates the maximum score of let’s say duplicate name values, such as “Chris” and “David” −
> db.demo114.group( ... {key: {Name:true}, ... reduce: function(c,p) { ... if (p.maximumScore < c.Score) { ... p.maximumScore = c.Score; ... } ... }, ... initial: { maximumScore: 0 }} ... );
This will produce the following output −
[ { "Name" : "Chris", "maximumScore" : 87 }, { "Name" : "David", "maximumScore" : 45 } ]
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