To rebuild indexes, use reIndex(). Let us first create an index. Following is the query −> db.demo42.createIndex({"StudentFirstName":1});This will produce the following output −{    "createdCollectionAutomatically" : true,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 }Following is the query to rebuild index in MongoDB −> db.demo42.reIndex({"StudentFirstName":1});This will produce the following output −{    "nIndexesWas" : 2,    "nIndexes" : 2,    "indexes" : [       {          "v" : 2,          "key" : {             "_id" : 1          },          "name" : "_id_",          "ns" : "web.demo42"       },       {          "v" : 2,          "key" : {             "StudentFirstName" : 1          },          "name" : "StudentFirstName_1",          "ns" : "web.demo42"       }   ],    "ok" : 1 }

To perform multiple write operations, use bulkWrite(). Let us create an array list values. Following is the query −> const arrayList = [ ...    {"Value1":100, "Value2":200, "Name": "John"}, ...    {"Value1":100, "Value2":200, "Name": "Bob"} ... ]; > let op1 = []; > arrayList.forEach(({ Value1, Value2, Name }) => { ...    op1.push({ ...       "updateOne": { ...          "filter": { Name}, ...          "update": { "$set": { Value1, Value2, Name } }, ...          "upsert": true ...       } ...    }) ... }); > db.demo397.bulkWrite(op1); ... Read More

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