Database
[{surname:"Will",lastname:"Smith",position:"Actor"},{surname:"Michael",lastname:"Jackson",position:"Musican"},{surname:"Will",lastname:"Smith",position:"Musican"},{surname:"Alicia",lastname:"Keys",position:"Musican"},{surname:"Brad",lastname:"Pitt",position:"Actor"}]
Query
db.collection.aggregate([{"$group":{"_id":{"surname":"$surname","lastname":"$lastname"},positions:{$addToSet:"$position"}}}])