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([{$group:{_id:null,data:{$addToSet:{CustName:"$CustName",CustNum:"$CustNum"}}}},{$unwind:"$data"},{$replaceRoot:{newRoot:"$data"}}])