You can use the following syntax to group by multiple fields and perform some aggregation in MongoDB:

db.collection.aggregate([
    {$group : {_id:{field1:"$field1", field2:"$field2"}, count:{$sum:1}}}
])

The following examples show how to use this syntax with a collection teams with the following documents:

db.teams.insertOne({team: "Mavs", position: "Guard", points: 31})db.teams.insertOne({team: "Mavs", position: "Guard", points: 22})db.teams.insertOne({team: "Mavs", position: "Forward", points: 19})db.teams.insertOne({team: "Rockets", position: "Guard", points: 26})db.teams.insertOne({team: "Rockets", position: "Forward", points: 33})

Example 1: Group By Multiple Fields & Aggregate

We can use the following code to group by ‘team’ and ‘position’ and count the occurrences of each grouping:

db.teams.aggregate([
    {$group : {_id:{team:"$team", position:"$position"}, count:{$sum:1}}}
])

This returns the following results:

{ _id: { team: 'Rockets', position: 'Forward' }, count: 1 }
{ _id: { team: 'Mavs', position: 'Guard' }, count: 2 }
{ _id: { team: 'Mavs', position: 'Forward' }, count: 1 }
{ _id: { team: 'Rockets', position: 'Guard' }, count: 1 }

We could also perform a different aggregation. For example, we could group by ‘team’ and position’ and find the sum of ‘points’ by grouping:

db.teams.aggregate([
    {$group : {_id:{team:"$team", position:"$position"}, sumPoints:{$sum:"$points"}}}])

This returns the following results:

{ _id: { team: 'Rockets', position: 'Forward' }, sumPoints: 33 }
{ _id: { team: 'Mavs', position: 'Guard' }, sumPoints: 53 }
{ _id: { team: 'Mavs', position: 'Forward' }, sumPoints: 19 }
{ _id: { team: 'Rockets', position: 'Guard' }, sumPoints: 26 }

This tells us:

• The sum of points scored by players on the ‘Rockets’ in position ‘Forward’ is 33.
• The sum of points scored by players on the ‘Mavs’ in position ‘Guard’ is 53.

And so on.

Example 2: Group By Multiple Fields & Aggregate (Then Sort)

db.teams.aggregate([
    {$group : {_id:{team:"$team", position:"$position"}, sumPoints:{$sum:"$points"}}},
    {$sort : {sumPoints:1}}
])

This returns the following results:

{ _id: { team: 'Mavs', position: 'Forward' }, sumPoints: 19 }
{ _id: { team: 'Rockets', position: 'Guard' }, sumPoints: 26 }
{ _id: { team: 'Rockets', position: 'Forward' }, sumPoints: 33 }
{ _id: { team: 'Mavs', position: 'Guard' }, sumPoints: 53 }

We can use -1 to instead sort the results by points in descending order:

db.teams.aggregate([
    {$group : {_id:{team:"$team", position:"$position"}, sumPoints:{$sum:"$points"}}},
    {$sort : {sumPoints:-1}}
])

This returns the following results:

{ _id: { team: 'Mavs', position: 'Guard' }, sumPoints: 53 }
{ _id: { team: 'Rockets', position: 'Forward' }, sumPoints: 33 }
{ _id: { team: 'Rockets', position: 'Guard' }, sumPoints: 26 }
{ _id: { team: 'Mavs', position: 'Forward' }, sumPoints: 19 }

Note: You can find the complete documentation for $group .