MongoDB order by two fields sum?

To order documents by the sum of two fields in MongoDB, use the aggregation framework with $project to calculate the sum and $sort to order the results.

Syntax

db.collection.aggregate([
    { $project: { field1: 1, field2: 1, sumField: { $add: ["$field1", "$field2"] } } },
    { $sort: { sumField: 1 } }  // 1 for ascending, -1 for descending
]);

Sample Data

db.orderByTwoFieldsDemo.insertMany([
    { "Value1": 10, "Value2": 35 },
    { "Value1": 12, "Value2": 5 },
    { "Value1": 55, "Value2": 65 }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("..."),
        ObjectId("..."),
        ObjectId("...")
    ]
}

db.orderByTwoFieldsDemo.find();

{
    "_id": ObjectId("5ca285576304881c5ce84baa"),
    "Value1": 10,
    "Value2": 35
}
{
    "_id": ObjectId("5ca2855f6304881c5ce84bab"),
    "Value1": 12,
    "Value2": 5
}
{
    "_id": ObjectId("5ca285686304881c5ce84bac"),
    "Value1": 55,
    "Value2": 65
}

Case 1: Ascending Order by Sum

Order documents by the sum of Value1 and Value2 in ascending order ?

db.orderByTwoFieldsDemo.aggregate([
    { $project: { Value1: 1, Value2: 1, orderBySumValue: { $add: ["$Value1", "$Value2"] } } },
    { $sort: { orderBySumValue: 1 } }
]);

{ "_id": ObjectId("5ca2855f6304881c5ce84bab"), "Value1": 12, "Value2": 5, "orderBySumValue": 17 }
{ "_id": ObjectId("5ca285576304881c5ce84baa"), "Value1": 10, "Value2": 35, "orderBySumValue": 45 }
{ "_id": ObjectId("5ca285686304881c5ce84bac"), "Value1": 55, "Value2": 65, "orderBySumValue": 120 }

Case 2: Descending Order by Sum

Order documents by the sum of Value1 and Value2 in descending order ?

db.orderByTwoFieldsDemo.aggregate([
    { $project: { Value1: 1, Value2: 1, orderBySumValue: { $add: ["$Value1", "$Value2"] } } },
    { $sort: { orderBySumValue: -1 } }
]);

{ "_id": ObjectId("5ca285686304881c5ce84bac"), "Value1": 55, "Value2": 65, "orderBySumValue": 120 }
{ "_id": ObjectId("5ca285576304881c5ce84baa"), "Value1": 10, "Value2": 35, "orderBySumValue": 45 }
{ "_id": ObjectId("5ca2855f6304881c5ce84bab"), "Value1": 12, "Value2": 5, "orderBySumValue": 17 }

Key Points

• $project stage calculates the sum using $add operator and creates a new field
• $sort stage orders documents by the calculated sum field
• Use 1 for ascending order and -1 for descending order

Conclusion

MongoDB aggregation framework with $project and $sort stages effectively orders documents by the sum of two fields. The $add operator calculates the sum, and $sort arranges the results in the desired order.