How to increment a field in MongoDB?

To increment a field in MongoDB, use the $inc operator with the update() method. The $inc operator increases the numeric value of a field by a specified amount.

Syntax

db.collection.update(
    { "query": "criteria" },
    { $inc: { "fieldName": incrementValue } }
);

Sample Data

Let us create a collection with player scores ?

db.incrementDemo.insertMany([
    { "PlayerScore": 100 },
    { "PlayerScore": 290 },
    { "PlayerScore": 560 }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5cc81cdd8f9e6ff3eb0ce44e"),
        ObjectId("5cc81ce28f9e6ff3eb0ce44f"),
        ObjectId("5cc81ce68f9e6ff3eb0ce450")
    ]
}

Display all documents from the collection ?

db.incrementDemo.find().pretty();

{ "_id": ObjectId("5cc81cdd8f9e6ff3eb0ce44e"), "PlayerScore": 100 }
{ "_id": ObjectId("5cc81ce28f9e6ff3eb0ce44f"), "PlayerScore": 290 }
{ "_id": ObjectId("5cc81ce68f9e6ff3eb0ce450"), "PlayerScore": 560 }

Example: Increment Player Score

Increment the PlayerScore of the second document by 10 ?

db.incrementDemo.update(
    { "_id": ObjectId("5cc81ce28f9e6ff3eb0ce44f") },
    { $inc: { "PlayerScore": 10 } }
);

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

Verify the result ?

db.incrementDemo.find().pretty();

{ "_id": ObjectId("5cc81cdd8f9e6ff3eb0ce44e"), "PlayerScore": 100 }
{ "_id": ObjectId("5cc81ce28f9e6ff3eb0ce44f"), "PlayerScore": 300 }
{ "_id": ObjectId("5cc81ce68f9e6ff3eb0ce450"), "PlayerScore": 560 }

Key Points

• The $inc operator only works with numeric values (integers, floats).
• Use negative values to decrement: { $inc: { "field": -5 } }
• If the field doesn't exist, $inc creates it with the increment value.

Conclusion

The $inc operator provides an efficient way to increment numeric fields in MongoDB. It can both increase and decrease values, and automatically creates the field if it doesn't exist.