To group several fields, use $group in MongoDB. Let us create a collection with documents −> db.demo192.insertOne({"Name":"Chris", "Age":22}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3adb9f03d395bdc21346cd") } > db.demo192.insertOne({"Name":"David", "Age":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3adba103d395bdc21346ce") } > db.demo192.insertOne({"Name":"Chris", "Age":22}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3adba503d395bdc21346cf") } > db.demo192.insertOne({"Name":"Mike", "Age":24}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3adbbf03d395bdc21346d0") }Display all documents from a collection with the help of find() method −> db.demo192.find();This will produce the following output −{ "_id" : ObjectId("5e3adb9f03d395bdc21346cd"), "Name" : "Chris", "Age" : 22 } { "_id" : ObjectId("5e3adba103d395bdc21346ce"), ... Read More

To get values of cursor in MongoDB, use hasNext(). Let us create a collection with documents −> db.demo191.insertOne({"EmployeeId":1, "EmployeeName":"Chris Brown"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3ad95303d395bdc21346c5") } > db.demo191.insertOne({"EmployeeId":2, "EmployeeName":"David Miller"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3ad95f03d395bdc21346c6") } > db.demo191.insertOne({"EmployeeId":1, "EmployeeName":"John Doe"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3ad96803d395bdc21346c7") } > db.demo191.insertOne({"EmployeeId":1, "EmployeeName":"John Smith"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3ad97003d395bdc21346c8") }Display all documents from a collection with the help of find() method −> db.demo191.find();This will produce the following output −{ "_id" : ObjectId("5e3ad95303d395bdc21346c5"), "EmployeeId" : 1, "EmployeeName" : "Chris ... Read More

To implement aggregation with multiple keys, use aggregate() along with $group. Let us create a collection with documents −> db.demo190.insertOne( ...   { ... ...      "DueDate" : ISODate("2020-01-01"), ...      "Value" : 10, ...      "Name" : "Chris" ...   } ...); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3ad76403d395bdc21346bf") } > > db.demo190.insertOne( ...   { ... ...      "DueDate" : ISODate("2020-02-05"), ...      "Value" : 30, ...      "Name" : "David" ...   } ...); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3ad76403d395bdc21346c0") } > db.demo190.insertOne( ...   { ... Read More

To sort by the sum of specified object inside inner array, use $match along with $sort. Let us create a collection with documents −> db.demo189.insertOne( ...   { ...      "_id" : 100, ...      "List" : [ ...         { ...            "Value" : 10 ...         }, ..         .{ ...            "Value" : 20 ...         }, ...         { ...            "Value" : 10 ...     ... Read More

To find same value multiple times, use $where in MongoDB. Let us create a collection with documents −> db.demo188.insertOne( ...   { ...      "ListOfData":[ ...         {"Data": 100}, ...         {"Data": 200}, ...         {"Data": 100} ...      ] ...   } ...); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3ad1c203d395bdc21346bd") } > db.demo188.insertOne( ...   { ...      "ListOfData":[ ...         {"Data": 100}, ...         {"Data": 200}, ...         {"Data": 300} ...   } ...); { ... Read More

Let us first create a collection with documents −> db.demo187.insertOne( ...    { ...      "_id" : "101", ...      "Details" : [ ...         { "Subject" : "MongoDB" }, ...         { "Subject" : "MySQL" } ...      ] ...   } ...); { "acknowledged" : true, "insertedId" : "101" } > db.demo187.insertOne( ...   { ...      "_id" : "102", ...      "Details" : [ ...         { } ...      ] ...   } ...); { "acknowledged" : true, "insertedId" : "102" ... Read More

Let us first create a collection with documents −> db.demo186.insertOne({"UserEmailId":"JOHN@GMAIL.COM", "UserName":"John"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e399d769e4f06af55199808") } > db.demo186.insertOne({"UserEmailId":"chris@gmail.com", "UserName":"chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e399d879e4f06af55199809") } > db.demo186.insertOne({"UserEmailId":"DAVID@GMAIL.COM", "UserName":"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e399d979e4f06af5519980a") }Display all documents from a collection with the help of find() method −> db.demo186.find();This will produce the following output −{ "_id" : ObjectId("5e399d769e4f06af55199808"), "UserEmailId" : "JOHN@GMAIL.COM", "UserName" : "John" } { "_id" : ObjectId("5e399d879e4f06af55199809"), "UserEmailId" : "chris@gmail.com", "UserName" : "chris" } { "_id" : ObjectId("5e399d979e4f06af5519980a"), "UserEmailId" : "DAVID@GMAIL.COM", "UserName" : "David" }Following is the ... Read More

To fetch records with $or on the basis of existence, use $or along with $exists. Let us create a collection with documents −>db.demo185.insertOne({_id:101, details:{Name:"Chris", Score:78, Subjects:{"Name":"MySQL"}}}); { "acknowledged" : true, "insertedId" : 101 } > db.demo185.insertOne({_id:102, details:{Name:"Bob", Score:78}}); { "acknowledged" : true, "insertedId" : 102 } >db.demo185.insertOne({_id:103, details:{Name:"David", Score:78, Subjects:{"Name":"MongoDB"}}}); { "acknowledged" : true, "insertedId" : 103 }Display all documents from a collection with the help of find() method −> db.demo185.find();This will produce the following output −{ "_id" : 101, "details" : { "Name" : "Chris", "Score" : 78, "Subjects" : { "Name" : "MySQL" } } } { "_id" ... Read More

To count, you can also use aggregate() along with $sum. Let us create a collection with documents −> db.demo184.insertOne({"Names":["Chris", "David", "Bob"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3999fb9e4f06af55199805") } > db.demo184.insertOne({"Names":["Chris", "Mike"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e399a0d9e4f06af55199806") } > db.demo184.insertOne({"Names":["Chris", "Bob", "Carol"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e399a209e4f06af55199807") }Display all documents from a collection with the help of find() method −> db.demo184.find();This will produce the following output −{ "_id" : ObjectId("5e3999fb9e4f06af55199805"), "Names" : [ "Chris", "David", "Bob" ] } { "_id" : ObjectId("5e399a0d9e4f06af55199806"), "Names" : [ "Chris", "Mike" ] } { ... Read More

To display subdocuments in one line, use $unwind along with aggregate(). Let us create a collection with documents −> db.demo183.insertOne( ... { ...   "_id": "110", ...   "DueDate": ISODate("2020-02-04T01:10:42.000Z"), ...   "ProductDetails": [ ...      { ...         "ProductName": "Product-1", ...         "isAvailable": true ...      }, ...      { ...         "ProductName": "Product-2", ...         "isAvailable": false ...      } ...   ] ...   } ...); { "acknowledged" : true, "insertedId" : "110" }Display all documents from a collection with the ... Read More