How to search for a record (field) and then delete it in MongoDB?

To search for a field and then delete it in MongoDB, use $exists to find documents containing the field, then $unset to remove it. The $unset operator deletes a particular field from documents.

Syntax

db.collection.update(
    { "fieldName": { $exists: true } },
    { $unset: { "fieldName": "" } },
    { multi: true }
);

Sample Data

Let us create a collection with documents ?

db.demo562.insertMany([
    { "Name": "Chris", "Age": 21 },
    { "Age": 20 },
    { "Name": "David", "Age": 23 }
]);

{
   "acknowledged" : true,
   "insertedIds" : [
      ObjectId("5e8f4ae854b4472ed3e8e872"),
      ObjectId("5e8f4ae954b4472ed3e8e873"),
      ObjectId("5e8f4aea54b4472ed3e8e874")
   ]
}

Display all documents from the collection ?

db.demo562.find();

{ "_id" : ObjectId("5e8f4ae854b4472ed3e8e872"), "Name" : "Chris", "Age" : 21 }
{ "_id" : ObjectId("5e8f4ae954b4472ed3e8e873"), "Age" : 20 }
{ "_id" : ObjectId("5e8f4aea54b4472ed3e8e874"), "Name" : "David", "Age" : 23 }

Example: Search and Delete Field

Search for documents with a "Name" field and delete that field ?

db.demo562.update(
    { Name: { $exists: true } },
    { $unset: { "Name": "" } },
    { multi: true }
);

WriteResult({ "nMatched" : 2, "nUpserted" : 0, "nModified" : 2 })

Verify Result

Display documents to confirm the "Name" field has been removed ?

db.demo562.find();

{ "_id" : ObjectId("5e8f4ae854b4472ed3e8e872"), "Age" : 21 }
{ "_id" : ObjectId("5e8f4ae954b4472ed3e8e873"), "Age" : 20 }
{ "_id" : ObjectId("5e8f4aea54b4472ed3e8e874"), "Age" : 23 }

Key Points

• $exists: true matches documents that contain the specified field.
• $unset removes the field entirely from matched documents.
• multi: true applies the operation to all matching documents.

Conclusion

Use $exists to search for documents containing a specific field, then $unset to remove that field. The multi: true option ensures all matching documents are updated in a single operation.