Database
[{"Id":"12345-7","Price":{"Base":"9.99","Promo":"7.99"},"Stock":[{"Code":"1","Qty":1.0},{"Code":"3","Qty":7.0}]},{"Id":"22222-0","Price":{"Base":"2.99","Promo":"2.99"},"Stock":[{"Code":"3","Qty":10.0},{"Code":"5","Qty":1.0},{"Code":"10","Qty":2.0}]}]
Query
db.collection.aggregate([{"$unwind":"$Stock"},{"$project":{item_id:"$Id",store:"$Stock.Code",price:"$Price.Base",quantity:"$Stock.Qty",sale_price:"$Price.Promo",}}])