MongoDB query which represents not equal to null or empty?

To set a query for not equal to null or empty, use the $nin operator. This operator selects documents where the field value is not in the specified array of values, effectively filtering out null and empty string values.

Syntax

db.yourCollectionName.find({yourFieldName: {$nin: [null, ""]}});

Sample Data

db.notEqualToNullOrEmptyDemo.insertMany([
    {"UserName": "Larry", "UserAge": 24},
    {"UserName": "", "UserAge": 29},
    {"UserName": "Sam", "UserAge": 32},
    {"UserName": null, "UserAge": 27},
    {"UserName": "Robert", "UserAge": 26},
    {"UserName": "", "UserAge": 23}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c9d20b6a629b87623db1b26"),
        ObjectId("5c9d20bea629b87623db1b27"),
        ObjectId("5c9d20c7a629b87623db1b28"),
        ObjectId("5c9d20d2a629b87623db1b29"),
        ObjectId("5c9d20dda629b87623db1b2a"),
        ObjectId("5c9d20e7a629b87623db1b2b")
    ]
}

Example: Filter Non-Null and Non-Empty Values

Query to find all documents where UserName is neither null nor empty ?

db.notEqualToNullOrEmptyDemo.find({UserName: {$nin: [null, ""]}});

{
    "_id": ObjectId("5c9d20b6a629b87623db1b26"),
    "UserName": "Larry",
    "UserAge": 24
}
{
    "_id": ObjectId("5c9d20c7a629b87623db1b28"),
    "UserName": "Sam",
    "UserAge": 32
}
{
    "_id": ObjectId("5c9d20dda629b87623db1b2a"),
    "UserName": "Robert",
    "UserAge": 26
}

Key Points

• $nin (not in) excludes documents where the field matches any value in the array.
• The array [null, ""] filters out both null values and empty strings.
• Only documents with actual string values will be returned.

Conclusion

Use $nin with [null, ""] to effectively query for fields that are not null or empty. This operator provides a clean way to filter out unwanted null and empty string values from your results.