For this, use $group in MongoDB. Within that, use $unwind, $group, $addToSet, etc. Let us create a collection with documents −> db.demo456.insertOne( ... { _id: 101, StudentName: ["Chris", "David"] } ... ); { "acknowledged" : true, "insertedId" : 101 } > > db.demo456.insertOne( ... { _id: 102, StudentName: ["Mike", "Sam"] } ... ); { "acknowledged" : true, "insertedId" : 102 } > db.demo456.insertOne( ... { _id: 103, StudentName: ["John", "Jace"] } ... ); { "acknowledged" : true, "insertedId" : 103 } > db.demo456.insertOne( ... { _id: 104, StudentName: ["Robert", "John"] } ... ); { "acknowledged" : true, "insertedId" : 104 ... Read More

To display a list of objects based on a specific property, use dot notation in find(). Let us create a collection with documents −> db.demo455.insertOne({"Information":{"Student":[{"Name":"Chris", "Age":22}]}});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7e1876dbcb9adb296c95c5") } > db.demo455.insertOne({"Information":{"Student":[{"Name":"David", "Age":21}]}});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7e1883dbcb9adb296c95c6") } > db.demo455.insertOne({"Information":{"Student":[{"Name":"Bob", "Age":24}]}});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7e188adbcb9adb296c95c7") } > db.demo455.insertOne({"Information":{"Student":[{"Name":"Robert", "Age":21}]}});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7e18bcdbcb9adb296c95c8") }Display all documents from a collection with the help of find() method −> db.demo455.find();This will produce the following output −{ "_id" : ObjectId("5e7e1876dbcb9adb296c95c5"), "Information" : { "Student" : [ { ... Read More

To publish the latest N records with sorting, use sort() along with limit(). Here, set the number of records you want to show with limit(). Let us create a collection with documents −> db.demo454.insertOne({"ClientName":"Chris"});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7cce8cdbcb9adb296c95c0") } > db.demo454.insertOne({"ClientName":"John"});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7cce95dbcb9adb296c95c1") } > db.demo454.insertOne({"ClientName":"Bob"});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7cce9fdbcb9adb296c95c2") } > db.demo454.insertOne({"ClientName":"David"});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7ccea6dbcb9adb296c95c3") } > db.demo454.insertOne({"ClientName":"Mike"});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7cceafdbcb9adb296c95c4") }Display all documents from a collection with the help of find() method −> db.demo454.find();This ... Read More

To filter documents based on an array, use $elemMatch. The $elemMatch operator matches documents that contain an array field.Let us create a collection with documents −> db.demo453.insertOne( ... { _id: 101, details: [ { Name: "David", Marks: 60 }, { Name: "Mike", Marks: 55} ] } ... ) { "acknowledged" : true, "insertedId" : 101 } > db.demo453.insertOne( ... { _id: 102, details: [ { Name: "Bob", Marks: 80 }, { Name: "Sam", Marks: 78} ] } ... ) { "acknowledged" : true, "insertedId" : 102 } > db.demo453.insertOne( ... { _id: 103, details: [ { Name: "Carol", Marks: 67 ... Read More

To get the count of repeated values in different documents, use aggregate(). Let us create a collection with documents −> db.demo452.insertOne({"StudentName":"John", "StudentAge":21});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7b7e3371f552a0ebb0a6f3") } > db.demo452.insertOne({"StudentName":"John", "StudentAge":22});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7b7e3671f552a0ebb0a6f4") } > db.demo452.insertOne({"StudentName":"John", "StudentAge":23});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7b7e3971f552a0ebb0a6f5") } > db.demo452.insertOne({"StudentName":"David", "StudentAge":24});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7b7e4371f552a0ebb0a6f6") } > db.demo452.insertOne({"StudentName":"David", "StudentAge":25});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7b7e4571f552a0ebb0a6f7") }Display all documents from a collection with the help of find() method −> db.demo452.find();This will produce the following output −{ "_id" : ... Read More

To get the mean daily average count of recorded documents, use aggregate(). Within that, use $project and $group.Let us create a collection with documents −Example> db.demo451.insertOne({ ... DueDate:new ISODate("2020-03-15T10:50:35.000Z"), ... Value: 10 ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e7b5c5d71f552a0ebb0a6e9") } > db.demo451.insertOne({ ... DueDate:new ISODate("2020-03-14T10:50:35.000Z"), ... Value: 10 ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e7b5c5d71f552a0ebb0a6ea") } > db.demo451.insertOne({ ... DueDate:new ISODate("2020-03-13T10:50:35.000Z"), ... Value: 10 ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e7b5c5d71f552a0ebb0a6eb") }Display all documents from a collection with the help of find() ... Read More

In order to reach subdata, you need to use key in MongoDB. Let us create a collection with documents −>db.demo450.insertOne({"Information":{"StudentDetails":{"StudentName":"Chris", "StudentAge":21}}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e7b590e71f552a0ebb0a6e6") } >db.demo450.insertOne({"Information":{"StudentDetails":{"StudentName":"David", "StudentAge":23}}});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7b591a71f552a0ebb0a6e7") } >db.demo450.insertOne({"Information":{"StudentDetails":{"StudentName":"Mike", "StudentAge":22}}});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7b592271f552a0ebb0a6e8") }Display all documents from a collection with the help of find() method −> db.demo450.find();This will produce the following output −{ "_id" : ObjectId("5e7b590e71f552a0ebb0a6e6"), "Information" : { "StudentDetails" : { "StudentName" : "Chris", "StudentAge" : 21 } } } { "_id" : ObjectId("5e7b591a71f552a0ebb0a6e7"), "Information" : { "StudentDetails" : { ... Read More

To insert an item to an already created array inside an object, use MongoDB $push. Let us create a collection with documents −> db.demo449.insertOne( ... { ...    details1: { ...       details2: [{ ...          _id:new ObjectId(), ...             Name:"Chris" ...       }], ...       details3: [{ ...          _id:new ObjectId(), ...          Name:"David" ...       }] ...    } ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e7a40e971f552a0ebb0a6e3") }Display all documents from ... Read More

The findOneAndDelete() deletes single documents from the collection on the basis of a filter and sort criteria as well as it returns the deleted document.The deleteOne() removes single document from the collection.Let us see an example and create a collection with documents −> db.demo448.insertOne({"Name":"Chris", "Age":21});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7a291cbbc41e36cc3caeca") } > db.demo448.insertOne({"Name":"David", "Age":23});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7a2926bbc41e36cc3caecb") } > db.demo448.insertOne({"Name":"Bob", "Age":22});{    "acknowledged" : true,    "insertedId" : ObjectId("5e7a2930bbc41e36cc3caecc") }Display all documents from a collection with the help of find() method −> db.demo448.find();This will produce the following output −{ "_id" : ObjectId("5e7a291cbbc41e36cc3caeca"), ... Read More

Inverted Index and Forward Index are data structures used to search text in a document or set of documents.Inverted IndexInverted Index stores the words as index and document name(s) as mapped reference(s).Forward IndexForward Index stores the document name as index and word(s) as mapped reference(s).The following are some of the important differences between the Inverted Index and Forward Index.Sr. No.KeyInverted IndexForward Index1Mapping PatternInverted Index stores the words as index and document name(s) as mapped reference(s).Forward Index stores the document name as index and word(s) as mapped reference(s).2Index Building ProcessScan the document, prepare a list of unique words.Prepare a list of ... Read More