If you try to add a number to undefined value then you will get a NaN. The NaN defines Not a Number. Following is an example −Case 1var anyVar=10+undefined; print(anyVar) //Result will be NaNCase 2var anyVar1=10; var anyVar2; var anyVar=yourVar1+yourVar2; print(anyVar) //Result will be NaNCase 1Let us implement the above ... Read More

To count the documents, use $count. For values beginning with 13, use $regex. You can use $regex. Let us create a collection with documents −> db.demo570.insertOne({Information:{Value:"13675"}});{    "acknowledged" : true, "insertedId" : ObjectId("5e90959b39cfeaaf0b97b583") } > db.demo570.insertOne({Information:{Value:"14135"}});{    "acknowledged" : true, "insertedId" : ObjectId("5e9095a739cfeaaf0b97b584") } > db.demo570.insertOne({Information:{Value:"15113"}});{    "acknowledged" : true, ... Read More

Let us create a collection with documents −> db.demo568.insertOne({ _id: 101, details: [ {id : 101 }, { id:103 } ] }); { "acknowledged" : true, "insertedId" : 101 }Display all documents from a collection with the help of find() method −> db.demo568.find();This will produce the following output −{ "_id" ... Read More

Set the fields you don’t want to include as 0 as in the below syntax. Here, we have set fields “yourFieldName1” and “yourFieldName2” as 0 −db.yourCollectionName.find(yourQuery, {yourFieldName1:0, yourFieldName2:0});To understand the above syntax, let us create a collection with documents −> db.demo567.insertOne({"Name":"Chris", Age:21});{    "acknowledged" : true, "insertedId" : ObjectId("5e908fa139cfeaaf0b97b57b") } ... Read More

To group the array items, use $group along with $sort. Let us create a collection with documents −> db.demo566.insertOne( ... { ... ...    "ProductInformation" : [ ...       { ...          "ProductName" : "Product-1", ...          "ProductPrice" :100 ...     ... Read More

To access fields in a document, simply use find(). Let us create a collection with documents −> db.demo565.insertOne( ... { ...    id:101, ...    Name:"David", ...    "CountryName":"US" ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e90896739cfeaaf0b97b577") } > > db.demo565.insertOne( ... { ...   ... Read More

To replace, use $set and positional($) operator. Let us create a collection with documents −> db.demo564.insertOne({"StudentName":["Chris", "David", "Mike", "Sam"]});{    "acknowledged" : true, "insertedId" : ObjectId("5e90880a39cfeaaf0b97b576") }Display all documents from a collection with the help of find() method −> db.demo564.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e90880a39cfeaaf0b97b576"), ... Read More

To get items with a specific value, simply use find(). Let us create a collection with documents −> db.demo563.insertOne({"Name":"Chris", "Age":21, "isMarried":true}){    "acknowledged" : true, "insertedId" : ObjectId("5e8f546c54b4472ed3e8e878") } > db.demo563.insertOne({"Name":"Bob", "Age":23, "isMarried":false}){    "acknowledged" : true, "insertedId" : ObjectId("5e8f547854b4472ed3e8e879") } > db.demo563.insertOne({"Name":"Carol", "Age":23, "isMarried":true}){    "acknowledged" : true, "insertedId" ... Read More

To search for a field, use $exists and to delete it, use $unset. The $unset operator in MongoDB deletes a particular field.Let us create a collection with documents −> db.demo562.insertOne({"Name":"Chris", "Age":21});{    "acknowledged" : true,    "insertedId" : ObjectId("5e8f4ae854b4472ed3e8e872") } > db.demo562.insertOne({"Age":20});{    "acknowledged" : true,    "insertedId" : ObjectId("5e8f4ae954b4472ed3e8e873") ... Read More

To randomize unique data, use Math.random() in MongoDB. Let us create a collection with documents −> db.demo561.insertOne({EmailId:null});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f490454b4472ed3e8e86c") } > db.demo561.insertOne({EmailId:null});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f490654b4472ed3e8e86d") } > db.demo561.insertOne({EmailId:null});{    "acknowledged" : true, "insertedId" : ObjectId("5e8f490a54b4472ed3e8e86e") }Display all documents from a collection ... Read More