To count the number of documents from the collection inside the array, use aggregate(). Let us create a collection with documents −> db.demo332.insertOne({details:[{Name:"Chris", Age:21}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e521f16f8647eb59e56208e") } > db.demo332.insertOne({details:[{Name:"David", Age:23}, {Name:"Bob", Age:22}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e521f21f8647eb59e56208f") }Display all documents from a collection with the help of find() method −> db.demo332.find();This will produce the following output −{ "_id" : ObjectId("5e521f16f8647eb59e56208e"), "details" : [ { "Name" : "Chris", "Age" : 21 } ] } { "_id" : ObjectId("5e521f21f8647eb59e56208f"), "details" : [ { "Name" : "David", "Age" : 23 }, { ... Read More

Let us create a collection with documents −> db.demo331.insertOne({"Words":"This is a MySQL"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e521c35f8647eb59e562089") } > db.demo331.insertOne({"Words":"THIS is a MongoDB"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e521c36f8647eb59e56208a") }Display all documents from a collection with the help of find() method−> db.demo331.find();This will produce the following output −{ "_id" : ObjectId("5e521c35f8647eb59e562089"), "Words" : "This is a MySQL" } { "_id" : ObjectId("5e521c36f8647eb59e56208a"), "Words" : "THIS is a MongoDB" }Following is the query to create an index for text search −> db.demo331.createIndex( {Words: "text" } ); {    "createdCollectionAutomatically" : false,    "numIndexesBefore" : ... Read More

To restrict returned data, use find(). The values 0 and 1 for fields would decide what all field values would be visible or hidden.Let us create a collection with documents −> db.demo330.insertOne({"Id":101, "Name":"Chris", "Age":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e52149ff8647eb59e562081") } > db.demo330.insertOne({"Id":102, "Name":"Sam", "Age":24}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5214aaf8647eb59e562082") } > db.demo330.insertOne({"Id":103, "Name":"David", "Age":28}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e5214b3f8647eb59e562083") } > db.demo330.insertOne({"Id":104, "Name":"Bob", "Age":23}); . {    "acknowledged" : true,    "insertedId" : ObjectId("5e5214bdf8647eb59e562084") }Display all documents from a collection with the help of find() method −> db.demo330.find();This ... Read More

For this, use $match along with aggregate(). Let us create a collection with documents −> db.demo329.insertOne({"Name":"Chris", "Age":21, "Marks":45}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516f28f8647eb59e56207d") } > db.demo329.insertOne({"Name":"David", "Age":21, "Marks":56}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516f28f8647eb59e56207e") } > db.demo329.insertOne({"Name":"Mike", "Age":21, "Marks":78}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516f29f8647eb59e56207f") } > db.demo329.insertOne({"Name":"David", "Age":21, "Marks":89}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516f29f8647eb59e562080") }Display all documents from a collection with the help of find() method −> db.demo329.find().pretty();This will produce the following output:{    "_id" : ObjectId("5e516f28f8647eb59e56207d"),    "Name" : "Chris",    "Age" : 21, ... Read More

The findOneAndUpdate() is used to update a single document based on the filter and sort criteria i.e. −db.collection.findOneAndUpdate(filter, update, options)Let us create a collection with documents −> db.demo328.insertOne({Name:"Chris", Marks:67}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516b19f8647eb59e56207a") } > db.demo328.insertOne({Name:"David", Marks:78}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516b24f8647eb59e56207b") } > db.demo328.insertOne({Name:"Bob", Marks:97}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516b2bf8647eb59e56207c") }Display all documents from a collection with the help of find() method −> db.demo328.find();This will produce the following output −{ "_id" : ObjectId("5e516b19f8647eb59e56207a"), "Name" : "Chris", "Marks" : 67 } { "_id" : ObjectId("5e516b24f8647eb59e56207b"), "Name" : ... Read More

For user-defined variables, use var keyword in MongoDB. Let us create a collection with documents −> db.demo327.insertOne({"FirstName":"Chris", "LastName":"Brown"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516952f8647eb59e562076") } > db.demo327.insertOne({"FirstName":"David", "LastName":"Miller"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e51695af8647eb59e562077") } > db.demo327.insertOne({"FirstName":"John", "LastName":"Doe"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516962f8647eb59e562078") } > db.demo327.insertOne({"FirstName":"John", "LastName":"Smith"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516968f8647eb59e562079") }Display all documents from a collection with the help of find() method −> db.demo327.find();This will produce the following output −{ "_id" : ObjectId("5e516952f8647eb59e562076"), "FirstName" : "Chris", "LastName" : "Brown" } { "_id" : ObjectId("5e51695af8647eb59e562077"), ... Read More

To access array values, use dot(.) notation. Let us create a collection with documents −> db.demo326.insertOne({id:101, "ProductDetails":[{"ProductId":"Prod-101", "ProductName":"Product-1"}, ... {"ProductId":"Prod-102", "ProductName":"Product-2"} ... ] ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516751f8647eb59e562074") } > db.demo326.insertOne({id:103, "ProductDetails":[{"ProductId":"Prod-104", "ProductName":"Product-5"}, ... {"ProductId":"Prod-105", "ProductName":"Product-6"} ... ] ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516771f8647eb59e562075") }Display all documents from a collection with the help of find() method −> db.demo326.find();This will produce the following output −{    "_id" : ObjectId("5e516751f8647eb59e562074"), "id" : 101, "ProductDetails" : [       { "ProductId" : "Prod-101", "ProductName" : "Product-1" }, ... Read More

Use insertMany() to insert multiple documents into a collection. With that, to update performance you can use ensureIndex().Let us create a collection with documents and insert multiple documents −> db.demo325.insertMany( [ ...    { _id: 101, Name: "Chris", Age: 23 }, ...    { _id: 102, Name: "David", Age: 24 }, ...    { _id: 103, Name: "Bob", Age: 22 } ... ] ); { "acknowledged" : true, "insertedIds" : [ 101, 102, 103 ] }Display all documents from a collection with the help of find() method −> db.demo325.find().pretty();This will produce the following output −{ "_id" : 101, "Name" : "Chris", "Age" : 23 } { "_id" : 102, "Name" : "David", "Age" : 24 } { "_id" : 103, "Name" : "Bob", "Age" : 22 }Using ensureIndex() −> db.demo325.ensureIndex({Name:1});This will produce the following output −{    "createdCollectionAutomatically" : false,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 }

Let us create a collection with documents −> db.demo324.insertOne({"ListOfValues":[10, 20, 30]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e516349f8647eb59e562073") }Display all documents from a collection with the help of find() method −> db.demo324.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e516349f8647eb59e562073"),    "ListOfValues" : [       10,       20,       30    ] }Here is the query displaying how to use positional operator −> db.demo324.update({"ListOfValues":[10, 20, 30]}, { $set: { "ListOfValues.$[]": "MongoDB" } }, { upsert: true } ); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Display all ... Read More

At first, let us create a collection with documents and also use ensureIndex() to create an index −> db.demo323.insertOne({"details":{"Name":"Chris", "Age":34}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e51157af8647eb59e56206e") } > db.demo323.insertOne({"details":{"Name":"David", "Age":31}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e511581f8647eb59e56206f") } > db.demo323.insertOne({"details":{"Name":"Bob", "Age":28}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e511589f8647eb59e562070") } > db.demo323.ensureIndex({"details.Name":1}); {    "createdCollectionAutomatically" : false,    "numIndexesBefore" : 2,    "numIndexesAfter" : 3,    "ok" : 1 }Display all documents from a collection with the help of find() method −> db.demo323.find();This will produce the following output −{ "_id" : ObjectId("5e51157af8647eb59e56206e"), "details" : ... Read More