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How to project grouping into object in MongoDB and display only the marks field?
Let us first create a document −
> var document= [ ... { "SubjectName" : "MySQL", "Marks" : 78 }, ... { "SubjectName" : "MongoDB", "Marks" : 89 }, ... { "SubjectName" : "Java", "Marks" : 71 }, ... ];
Following is the query to display document −
> printjson(document);
This will produce the following output −
[ { "SubjectName" : "MySQL", "Marks" : 78 }, { "SubjectName" : "MongoDB", "Marks" : 89 }, { "SubjectName" : "Java", "Marks" : 71 } ]
Following is the query to project grouping into an object in MongoDB −
> var makeObject= {}; > document.forEach(function (d){ ... makeObject[d.SubjectName] = d.Marks; ... }); > printjson(makeObject);
This will produce the following output −
{ "MySQL" : 78, "MongoDB" : 89, "Java" : 71 }
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