How to remove key fields in MongoDB?

To remove key fields in MongoFB, you can use $unset operator. Let us first create a collection with documents −

>db.removeKeyFieldsDemo.insertOne({"StudentFirstName":"John","StudentLastName":"Doe","StudentAge":23}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cc6c8289cb58ca2b005e672") } >db.removeKeyFieldsDemo.insertOne({"StudentFirstName":"John","StudentLastName":"Smith","StudentAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cc6c8359cb58ca2b005e673") }

Following is the query to display all documents from a collection with the help of find() method −

> db.removeKeyFieldsDemo.find().pretty();

This will produce the following output −

{    "_id" : ObjectId("5cc6c8289cb58ca2b005e672"),    "StudentFirstName" : "John",    "StudentLastName" : "Doe",    "StudentAge" : 23 } {    "_id" : ObjectId("5cc6c8359cb58ca2b005e673"),    "StudentFirstName" : "John",    "StudentLastName" : "Smith",    "StudentAge" : 21 }

Following is the query to remove key fields. Here, we are removing the StudentAge −

> db.removeKeyFieldsDemo.updateMany({},{$unset:{StudentAge:1}}); { "acknowledged" : true, "matchedCount" : 2, "modifiedCount" : 2 }

Let us display all documents from the above collection −

> db.removeKeyFieldsDemo.find().pretty();

This will produce the following output −

{    "_id" : ObjectId("5cc6c8289cb58ca2b005e672"),    "StudentFirstName" : "John",    "StudentLastName" : "Doe" } {    "_id" : ObjectId("5cc6c8359cb58ca2b005e673"),    "StudentFirstName" : "John",    "StudentLastName" : "Smith" }