db={"Merchant":[{"_id":ObjectId("628728cf9f5c99d8dedbe759"),"name":"agriTales","information":"Farmers social","categories":[ObjectId("6287220c52497922d6f4a121")],"website":"www.agritales.com","active":true}],"LuckyDraw":[{"_id":ObjectId("62873487e0e5eedc24748a55"),"business":ObjectId("628728cf9f5c99d8dedbe759"),"title":"May Lucky draw 2022","date_start":ISODate("2022-04-26T00:00:00Z"),"max_participants":5,"active":true,"date_of_draw":ISODate("2022-07-30T00:00:00Z"),"prizes_winners":[{"prize_name":"1st Prize","coupon_voucher":ObjectId("62872f809f5c99d8dedbe764")},{"prize_name":"2nd Prize","coupon_voucher":ObjectId("62872f8d9f5c99d8dedbe765")}],"result_declared":true}],"CouponVoucher":[{"_id":ObjectId("62872f809f5c99d8dedbe764"),"business":ObjectId("628728cf9f5c99d8dedbe759"),"type":"voucher","title":"8farmers Coupons 2001","minimum_order_value":0,"voucher_face_value":2001,"active":true,"status":"NEW","date_expiry":ISODate("2022-12-31T00:00:00Z"),},{"_id":ObjectId("62872f8d9f5c99d8dedbe765"),"type":"voucher","title":"8farmers Coupons 1501","minimum_order_value":0,"voucher_face_value":1501,"active":true,"status":"NEW","date_expiry":ISODate("2022-12-31T00:00:00Z")}]}

db.LuckyDraw.aggregate([{"$lookup":{"from":"Merchant","localField":"business","foreignField":"_id","pipeline":[{"$unset":["active","website"]}],"as":"business"}},{"$lookup":{"from":"CouponVoucher","localField":"prizes_winners.coupon_voucher","foreignField":"_id","let":{"prizes_winners":"$prizes_winners"},"pipeline":[{"$set":{"prize_name":{"$reduce":{"input":"$$prizes_winners","initialValue":"","in":{"$cond":[{"$eq":["$$this.coupon_voucher","$_id"]},"$$this.prize_name","$$value"]}}}}}],"as":"prizes_winners"}}])