For this, use $lookup. This performs a left outer join to an unsharded collection in the same database to filter in documents from the “joined” collection for processing.Let us first create a collection with documents −> db.demo395.insertOne({Name:"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5e782317aa3ef9ab8ab207") } > db.demo395.insertOne({Name:"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5e782317aa3ef9ab8ab208") }Display all documents from a collection with the help of find() method −> db.demo395.find();This will produce the following output −{ "_id" : ObjectId("5e5e782317aa3ef9ab8ab207"), "Name" : "Chris" } { "_id" : ObjectId("5e5e782317aa3ef9ab8ab208"), "Name" : "David" }Let us create a second collection with documents ... Read More

Let us first create a collection with documents −> db.demo394.insertOne( ...    { ... ...       details: [ ...       { ...          _id: '1', ...          startDate: '2018-01-11T07:00:00.000Z', ...          endDate: '2019-01-12T07:59:59.999Z' ...       }, ...       { ...          _id: '2', ...          startDate: '2019-01-21T07:00:00.000Z', ...          endDate: '2020-01-04T07:59:59.999Z' ...       } ...    ] ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5e716817aa3ef9ab8ab202") }Display all ... Read More

For this, use aggregate(). Let us first create a collection with documents −> db.demo393.insertOne( ...    { ...       Id1: "1", ...       Name: "Chris", ...       Id2: "100" ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5e6dd522064be7ab44e804") } > db.demo393.insertOne( ...    { ...       Id1: "1", ...       Name: "Chris", ...       Id2: "101" ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5e6dd522064be7ab44e805") } > db.demo393.insertOne( ...    { ...       Id1: "3", ... ... Read More

To pull values, use $pull and set multi: true. Let us first create a collection with documents −> db.demo392.insertOne( ...    { ...       Name: 'Chris', ...       details: [ ...          { ...             _id: '101' ... ...          }, ...          { ...             _id: '102' ...          } ...       ] ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5d2b3322064be7ab44e802") } > > db.demo392.insertOne( ... Read More

To get a single element, use aggregation and LIMIT. The skip() is used to skip a specific number of documents.Let us first create a collection with documents −> db.demo391.insertOne( ...    { "_id" : 101, "Name" : "Chris", Values: ["101", "102"] } ... ) { "acknowledged" : true, "insertedId" : 101 } > db.demo391.insertOne( ...    { "_id" : 111, "Name" : "Chris", Values: ["101", "102"] } ... ) { "acknowledged" : true, "insertedId" : 111 } > db.demo391.insertOne( ...    { "_id" : 121, "Name" : "Chris", Values: ["101", "102"] } ... ) { "acknowledged" : true, "insertedId" : ... Read More

You need to set multi to true. Include the option multi − true to update all documents that match the query criteria.Let us first create a collection with documents −> db.demo390.insertOne({"FirstName":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5d1f3a22064be7ab44e7fa") } > db.demo390.insertOne({"FirstName":"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5d1f3e22064be7ab44e7fb") } > db.demo390.insertOne({"FirstName":"Bob"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5d1f4122064be7ab44e7fc") } > db.demo390.insertOne({"FirstName":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5d1f4422064be7ab44e7fd") }Display all documents from a collection with the help of find() method −> db.demo390.find();This will produce the following output −{ "_id" : ObjectId("5e5d1f3a22064be7ab44e7fa"), "FirstName" ... Read More

Let us first create a collection with documents −> db.demo389.insertOne( ...    { ...       "details":[ ...          { ...             "Name":[ ...                "Chris", ...                "David" ...             ] ...          }, ...          { ...             "Name":[ ...                "Bob", ...                "Mike" ...       ... Read More

To remove, use $pull in MongoDB. Let us first create a collection with documents −> db.demo388.insertOne( ...    { ...       _id: '101', ...       userDetails: { ...          isMarried: false, ...          userInfo: [ ...             { ...                Name:"Chris", ...                Age:21 ... ...             } ...          ] ...       } ...    } ... ); { "acknowledged" : true, ... Read More

To unwind, means to deconstruct an array field from the input documents to output a document for each element.To unwind arrays, use $unwind in MongoDB aggregation. Let us first create a collection with documents −> db.demo387.insertOne( ...    { ... ...       "Name" : "101", ...       "Details1" : [ ...          {Value:100, Value1:50, Value2:40}, ...          {Value:200}, ...          {Value:300} ...       ], ...       "Details" : [ ...          {Value:100, Value1:30, Value2:26}, ...          {Value:200}, ... Read More

Let us first create a collection with documents −> db.demo386.insert( ...    { ...       details: { Month: 02, Day: 27, Year: 2020 } ...    } ... ); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo386.find();This will produce the following output −{ "_id" : ObjectId("5e5bd9a222064be7ab44e7f7"), "details" : { "Month" : 2, "Day" : 27, "Year" : 2020 } }Following is the query to convert date parts to date −> db.demo386.aggregate( ...    {"$project":{ ...       "_id":0, ...       "DueDate":{ ...          "$dateToString":{ ...             "format":"%m-%d-%Y", ...             "date":{"$dateFromParts": {"year":"$details.Year","month":"$details.Month","day":"$details.Day"}} ...          } ...       } ...    }} ... );This will produce the following output −{ "DueDate" : "02-27-2020" }