How to query for records where field is null or not set in MongoDB?

In MongoDB, you can query for records where a field is null or not set using different operators. There are two distinct cases: when a field exists but is set to null, and when a field doesn't exist in the document at all.

Syntax

// Field exists and is null
db.collection.find({"fieldName": null});

// Field does not exist
db.collection.find({"fieldName": {$exists: false}});

// Field is null OR does not exist
db.collection.find({$or: [{"fieldName": null}, {"fieldName": {$exists: false}}]});

Sample Data

db.fieldIsNullOrNotSetDemo.insertMany([
    {"EmployeeName": "Larry", "EmployeeAge": null, "EmployeeSalary": 18500},
    {"EmployeeName": "Bob", "EmployeeAge": 21, "EmployeeSalary": 23500},
    {"EmployeeName": "Carol", "EmployeeSalary": 45500},
    {"EmployeeName": "Mike", "EmployeeAge": null, "EmployeeSalary": 45500},
    {"EmployeeName": "Ramit", "EmployeeSalary": 85500}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("..."),
        ObjectId("..."),
        ObjectId("..."),
        ObjectId("..."),
        ObjectId("...")
    ]
}

Display all documents to see the data structure ?

db.fieldIsNullOrNotSetDemo.find().pretty();

{
    "_id": ObjectId("5c8a995c6cea1f28b7aa07fe"),
    "EmployeeName": "Larry",
    "EmployeeAge": null,
    "EmployeeSalary": 18500
}
{
    "_id": ObjectId("5c8a99836cea1f28b7aa07ff"),
    "EmployeeName": "Bob",
    "EmployeeAge": 21,
    "EmployeeSalary": 23500
}
{
    "_id": ObjectId("5c8a999b6cea1f28b7aa0800"),
    "EmployeeName": "Carol",
    "EmployeeSalary": 45500
}
{
    "_id": ObjectId("5c8a99bb6cea1f28b7aa0801"),
    "EmployeeName": "Mike",
    "EmployeeAge": null,
    "EmployeeSalary": 45500
}
{
    "_id": ObjectId("5c8a99d76cea1f28b7aa0802"),
    "EmployeeName": "Ramit",
    "EmployeeSalary": 85500
}

Case 1: Field is Present but Set to Null

Count documents where EmployeeAge field exists but is set to null ?

db.fieldIsNullOrNotSetDemo.count({EmployeeAge: null});

4

Note: This returns 4 because it matches both null values (Larry, Mike) AND missing fields (Carol, Ramit). MongoDB treats missing fields as null when using this syntax.

Case 2: Field Does Not Exist

Count documents where EmployeeAge field is completely missing ?

db.fieldIsNullOrNotSetDemo.count({EmployeeAge: {$exists: false}});

2

Method 3: Strict Null Check (Recommended)

To find only documents where a field exists and is explicitly set to null ?

db.fieldIsNullOrNotSetDemo.find({
    EmployeeAge: null,
    EmployeeAge: {$exists: true}
});

Key Points

• {field: null} matches both null values and missing fields
• {field: {$exists: false}} matches only missing fields
• {field: {$exists: true}} matches only existing fields (regardless of value)
• Combine operators for precise matching of your specific use case

Conclusion

Use {field: null} for broad null/missing queries, {$exists: false} for strictly missing fields, and combine both operators when you need precise control over null vs missing field matching.