Find items that do not have a certain field in MongoDB?

To find documents that do not have a certain field in MongoDB, use the $exists operator with the value false. This operator checks whether a field is present in the document, regardless of its value.

Syntax

db.collection.find({"fieldName": {$exists: false}})

Sample Data

Let's create a collection with documents where some have a specific field and others don't ?

db.findDocumentDoNotHaveCertainFields.insertMany([
    {"UserId": 101, "UserName": "John", "UserAge": 21},
    {"UserName": "David", "UserAge": 22, "UserFavouriteSubject": ["C", "Java"]},
    {"UserName": "Bob", "UserAge": 24, "UserFavouriteSubject": ["MongoDB", "MySQL"]}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c8a95fb6cea1f28b7aa07fb"),
        ObjectId("5c8a96116cea1f28b7aa07fc"),
        ObjectId("5c8a96306cea1f28b7aa07fd")
    ]
}

View All Documents

db.findDocumentDoNotHaveCertainFields.find().pretty()

{
    "_id": ObjectId("5c8a95fb6cea1f28b7aa07fb"),
    "UserId": 101,
    "UserName": "John",
    "UserAge": 21
}
{
    "_id": ObjectId("5c8a96116cea1f28b7aa07fc"),
    "UserName": "David",
    "UserAge": 22,
    "UserFavouriteSubject": ["C", "Java"]
}
{
    "_id": ObjectId("5c8a96306cea1f28b7aa07fd"),
    "UserName": "Bob",
    "UserAge": 24,
    "UserFavouriteSubject": ["MongoDB", "MySQL"]
}

Example: Find Documents Without UserFavouriteSubject

To find documents that do not have the "UserFavouriteSubject" field ?

db.findDocumentDoNotHaveCertainFields.find({"UserFavouriteSubject": {$exists: false}}).pretty()

{
    "_id": ObjectId("5c8a95fb6cea1f28b7aa07fb"),
    "UserId": 101,
    "UserName": "John",
    "UserAge": 21
}

Key Points

• $exists: false finds documents where the field is completely absent
• $exists: true finds documents where the field exists (even if null)
• This operator works with any field type and nested fields

Conclusion

The $exists operator with false value effectively filters documents that are missing specific fields. This is useful for data validation and finding incomplete records in your collection.