Sort by subdocument in MongoDB

To sort by subdocument, use $sort in MongoDB. Let us create a collection with documents −

> db.demo245.insertOne( ...   { ...      "_id": 101, ...      "deatils": [ ...         { "DueDate": new ISODate("2019-01-10"), "Value": 45}, ...         {"DueDate": new ISODate("2019-11-10"), "Value": 34 } ...      ] ...   } ...); { "acknowledged" : true, "insertedId" : 101 } > db.demo245.insertOne( ...   { ...      "_id": 102, ...      "details": [ ...         { "DueDate": new ISODate("2019-12-11"), "Value": 29}, ...         {"DueDate": new ISODate("2019-03-10"), "Value":  78} ...      ] ...   } ...); { "acknowledged" : true, "insertedId" : 102 }

Display all documents from a collection with the help of find() method −

> db.demo245.find();

This will produce the following output −

{    "_id" : 101, "deatils" : [       { "DueDate" : ISODate("2019-01-10T00:00:00Z"), "Value" : 45 },       { "DueDate" : ISODate("2019-11-10T00:00:00Z"), "Value" : 34 }    ] } {    "_id" : 102, "details" : [       { "DueDate" : ISODate("2019-12-11T00:00:00Z"), "Value" : 29 },       { "DueDate" : ISODate("2019-03-10T00:00:00Z"), "Value" : 78 } \    ] }

Following is the query to sort by subdocument −

> db.demo245.aggregate([ ...   { "$unwind": "$details" }, ...   { "$sort": { "_id": 1, "details.Value": -1 } }, ...   { "$group": { ...      "_id": "$_id", ...      "details": { "$push": "$details" } ...   }}, ...   { "$sort": { "details.Value": -1 } } ...])

This will produce the following output −

{ "_id" : 102, "details" : [ { "DueDate" : ISODate("2019-03-10T00:00:00Z"), "Value" : 78 }, { "DueDate" : ISODate("2019-12-11T00:00:00Z"), "Value" : 29 } ] }