Filter documents in MongoDB if all keys exist as fields?

To filter documents in MongoDB where all specified keys exist as fields in an array, use the $all operator. This operator matches documents containing all specified elements in the array, regardless of order.

Syntax

db.collection.find({
    "arrayField": { "$all": ["value1", "value2", "value3"] }
});

Sample Data

db.demo17.insertMany([
    {"ListOfSubject": ["MySQL", "MongoDB", "Java"]},
    {"ListOfSubject": ["C", "Python", "Java"]},
    {"ListOfSubject": ["C++", "MongoDB", "PL/SQL"]}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e13847255d0fc6657d21f0a"),
        ObjectId("5e13847e55d0fc6657d21f0b"),
        ObjectId("5e13849255d0fc6657d21f0c")
    ]
}

Verify Sample Data

db.demo17.find();

{ "_id": ObjectId("5e13847255d0fc6657d21f0a"), "ListOfSubject": ["MySQL", "MongoDB", "Java"] }
{ "_id": ObjectId("5e13847e55d0fc6657d21f0b"), "ListOfSubject": ["C", "Python", "Java"] }
{ "_id": ObjectId("5e13849255d0fc6657d21f0c"), "ListOfSubject": ["C++", "MongoDB", "PL/SQL"] }

Example: Filter with $all Operator

Find documents that contain all three subjects: "C++", "PL/SQL", and "MongoDB" ?

db.demo17.find({
    "ListOfSubject": { "$all": ["C++", "PL/SQL", "MongoDB"] }
});

{ "_id": ObjectId("5e13849255d0fc6657d21f0c"), "ListOfSubject": ["C++", "MongoDB", "PL/SQL"] }

Key Points

• The $all operator requires all specified values to be present in the array.
• Order of elements in the $all array doesn't matter.
• The target array can contain additional elements beyond those specified in $all.

Conclusion

Use $all to filter documents where an array field contains all specified values. This operator is perfect for "must have all" filtering scenarios in MongoDB arrays.