MongoDB – How to remove a field in Mongo Document

Today in this article, we shall learn MongoDB – How to remove a field in MongoDB using Mongo shell CLI or UI query.

We will cover various 3-4 approaches to perform the remove fields feature. Today overall, We will cover the below aspects,

The below approach discussed is very useful when you don’t want to delete or drop the Mongo collection but want to clear all existing documents based on certain matching criteria.

I have below Mongo Collection where my fields are defined as below.

I have a field name called “EmpID” which I want to delete this field using MongoShell

Let’s get started step by step with details on how to achieve rename.

Please open the command prompt or PowerShell and log in to your database using a connection string.

We will first log to MongoDB and then switch to using the required database and the collection

use <DBName>

Command Pattern

{ $unset: { <fieldName>:1} }

You can specify one or multiple fields for the renaming support.

Approach 1 – $unset Remove the field for all the documents in the database

Command:

db.employee.update( {}, { $unset: {'EmpID':1}},false,true )

Example

db.employee.update( {}, { $unset: {'EmpID':1}},false,true )
WriteResult({ "nMatched" : 4, "nUpserted" : 0, "nModified" : 4 })

Approach 2 – Remove the field for all documents in the MongoDB

Command:

db.employee.update( {}, { $unset: {'EmpID':1}},false,true )

Example

db.employee.update( {}, { $unset: {‘EmpID’:1}},false,true )
WriteResult({ “nMatched” : 4, “nUpserted” : 0, “nModified” : 4 })

Approach 3 – Remove the field for all documents in the database using updateMany

Using updateMany to Remove the field for all documents.

Command:

 db.employee.updateMany({},{"$unset":{"EmpID":1}})

Example

db.employee.updateMany({},{"$unset":{"empID":1}})
{ "acknowledged" : true, "matchedCount" : 4, "modifiedCount" : 4 }

Approach 4 – Remove the first field in documents in the database using updateOne

We can use updateOne with $unset query

Command:

 ddb.employee.updateOne( {}, { $unset: { EmpID:"" }})

Example

db.employee.updateOne( {}, { $unset: { EmpID:”” }})
{ “acknowledged” : true, “matchedCount” : 1, “modifiedCount” : 1 }

Approach 5 – Remove the first field based on matching filter criteria using updateOne

Below query removes the specified field if matches with a field for field name as “John”.

Command:

 db.employee.updateOne( {Name:"John"}, { $unset: { EmpID:"" }})

Example

db.employee.updateOne( {}, { $unset: { EmpID:”” }})
{ “acknowledged” : true, “matchedCount” : 1, “modifiedCount” : 1 }

If you are using an embedded document or in an array, use dot notation to specify the field name.

Delete records using the Delete or Remove method

Remove or Delete is yet another simple technique One can delete single or multiple records using delete() or remove() method too.

For more details please visit below,

• MongoDB query Delete records in a Collection using Delete() or Remove()

References:

• Create Drop MongoDB Collection

• Getting started with MongoDB ASP.NET Core

Do you have any comments or ideas or any better suggestions to share?

Please sound off your comments below.

Happy Coding !!

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