[{"categoryCode":"categoryCode1","categoryName":"categoryName1","cat_type":"A"},{"categoryCode":"categoryCode1","categoryName":"categoryName1","cat_type":"B"},{"categoryCode":"categoryCod2","categoryName":"categoryName2","cat_type":"B"}]

db.collection.aggregate([{"$group":{"_id":{"categoryCode":"$categoryCode","categoryName":"$categoryName",},"cat_type":{"$addToSet":"$cat_type"}},},{"$project":{"_id":0,"categoryCode":"$_id.categoryCode","categoryName":"$_id.categoryName","cat_type":"$cat_type"}},])