Database
[{"CustNum":101,"CustName":"Juan Dela Cruz"},{"CustNum":103,"CustName":"Jose Nicholas"},{"CustNum":101,"CustName":"Juan Dela Cruz"},{"CustNum":101,"CustName":"Juan Dela Cruz"},{"CustNum":101,"CustName":"Maria Makiling"}]
Query
db.collection.aggregate([{"$group":{"_id":"$CustName","CustName":{"$first":"$CustName"},"CustNum":{"$first":"$CustNum"},}}])