MongoDB query for documents whose array elements does not have a specific value

To query documents whose array elements do not have a specific value in MongoDB, use the $elemMatch operator combined with $exists: false. This finds documents containing arrays where at least one element lacks the specified field.

Syntax

db.collection.find({
    "arrayField": {
        "$elemMatch": {
            "fieldToCheck": { "$exists": false }
        }
    }
});

Sample Data

Let us create a collection with documents ?

db.demo239.insertMany([
    {
        "Name": "Chris",
        "details": [
            { "DueDate": new ISODate("2019-01-21"), "ProductPrice": 1270 },
            { "DueDate": new ISODate("2020-02-12"), "ProductPrice": 2000 }
        ]
    },
    {
        "Name": "David",
        "details": [
            { "DueDate": new ISODate("2018-11-11"), "ProductPrice": 1450 },
            { "DueDate": new ISODate("2020-02-12") }
        ]
    }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e441c6bf4cebbeaebec5157"),
        ObjectId("5e441c6cf4cebbeaebec5158")
    ]
}

Display all documents from the collection ?

db.demo239.find();

{
    "_id": ObjectId("5e441c6bf4cebbeaebec5157"),
    "Name": "Chris",
    "details": [
        { "DueDate": ISODate("2019-01-21T00:00:00Z"), "ProductPrice": 1270 },
        { "DueDate": ISODate("2020-02-12T00:00:00Z"), "ProductPrice": 2000 }
    ]
}
{
    "_id": ObjectId("5e441c6cf4cebbeaebec5158"),
    "Name": "David",
    "details": [
        { "DueDate": ISODate("2018-11-11T00:00:00Z"), "ProductPrice": 1450 },
        { "DueDate": ISODate("2020-02-12T00:00:00Z") }
    ]
}

Example: Find Documents Missing ProductPrice

Query documents where at least one array element lacks the ProductPrice field ?

db.demo239.find({
    "details": {
        "$elemMatch": {
            "DueDate": { "$exists": true },
            "ProductPrice": { "$exists": false }
        }
    }
});

{
    "_id": ObjectId("5e441c6cf4cebbeaebec5158"),
    "Name": "David",
    "details": [
        { "DueDate": ISODate("2018-11-11T00:00:00Z"), "ProductPrice": 1450 },
        { "DueDate": ISODate("2020-02-12T00:00:00Z") }
    ]
}

Key Points

• $elemMatch matches documents where at least one array element meets all specified conditions.
• $exists: false identifies array elements that lack a specific field.
• The query returns David's document because one of his detail elements is missing ProductPrice.

Conclusion

Use $elemMatch with $exists: false to find documents containing arrays where at least one element lacks a specific field. This approach efficiently identifies incomplete data within array structures.