Group by dates in a MongoDB collection?

To group by dates, use $group in MongoDB aggregate. Let us create a collection with documents −

> db.demo657.insertOne({ ...       id: 1, ...       Name: "Chris", ...       DueDate: new ISODate("2020-04-22") ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5ea064b44deddd72997713d6") } > db.demo657.insertOne( ... { ...    id: 1, ...    Name: "John", ...    DueDate: new ISODate("2020-04-22") ... } ...); {    "acknowledged" : true,    "insertedId" : ObjectId("5ea064b44deddd72997713d7") } > db.demo657.insertOne( ... { ...    id: 1, ...    Name: "Chris", ...    DueDate: new ISODate("2020-04-22") ... } ...); {    "acknowledged" : true,    "insertedId" : ObjectId("5ea064b44deddd72997713d8") }

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

> db.demo657.find();

This will produce the following output −

{ "_id" : ObjectId("5ea064b44deddd72997713d6"), "id" : 1, "Name" : "Chris", "DueDate" : ISODate("2020-04-22T00:00:00Z") } { "_id" : ObjectId("5ea064b44deddd72997713d7"), "id" : 1, "Name" : "John", "DueDate" : ISODate("2020-04-22T00:00:00Z") } { "_id" : ObjectId("5ea064b44deddd72997713d8"), "id" : 1, "Name" : "Chris", "DueDate" : ISODate("2020-04-22T00:00:00Z") }

Following is the query to group by dates in MongoDB collection −

> db.demo657.aggregate([ ...    {$match: {id:1, DueDate: {$gte:new ISODate('2020-04-21'), $lt:new ISODate   ("2020-04-23")}}}, ...    {$project: ...    {day: {'$dayOfMonth': '$DueDate'},month: {'$month':'$DueDate'},year: {'$year':'$DueDate'},Name:"$Name" } ... }, ...    {$group: { ...       _id: {day:'$day',month:'$month',year:'$year'}, ...       ListOfNames: {$push:{Name:'$Name'}} ...    }} ... ])

This will produce the following output −

{ "_id" : { "day" : 22, "month" : 4, "year" : 2020 }, "ListOfNames" : [ { "Name" : "Chris" }, { "Name" : "John" }, { "Name" : "Chris" } ] }