Removing an array element from MongoDB collection using update() and $pull

To remove a specific element from an array in MongoDB, use the $pull operator with the update() method. This operator removes all instances of a value that match the specified condition from an array field.

Syntax

db.collection.update(
    { query },
    { $pull: { "arrayField": "valueToRemove" } }
);

Create Sample Data

Let us first create a collection with documents ?

db.removingAnArrayElementDemo.insertOne({
    "UserMessage": ["Hi", "Hello", "Bye"]
});

{
    "acknowledged": true,
    "insertedId": ObjectId("5cef97bdef71edecf6a1f6a4")
}

Display all documents from a collection with the help of find() method ?

db.removingAnArrayElementDemo.find().pretty();

{
    "_id": ObjectId("5cef97bdef71edecf6a1f6a4"),
    "UserMessage": [
        "Hi",
        "Hello",
        "Bye"
    ]
}

Example: Remove Array Element

Following is the query to remove an array element from MongoDB ?

db.removingAnArrayElementDemo.update(
    { _id: ObjectId("5cef97bdef71edecf6a1f6a4") },
    { $pull: { "UserMessage": "Hello" } }
);

WriteResult({ "nMatched": 1, "nUpserted": 0, "nModified": 1 })

Verify Result

Let us check the document once again ?

db.removingAnArrayElementDemo.find().pretty();

{
    "_id": ObjectId("5cef97bdef71edecf6a1f6a4"),
    "UserMessage": [
        "Hi",
        "Bye"
    ]
}

Conclusion

The $pull operator successfully removes all matching elements from an array field. This operation modifies the document in place and is useful for cleaning up array data in MongoDB collections.