Database
[{"_id":123456,"key_stock":756159,"stock":"abc","code":"cba",qrtly_result:{"30/01/2000":{"item1":"123","item2":"321","item3":"987",}}}]
Query
db.collection.update({"key_stock":756159},{"$set":{"qrtly_result":{"30/09/2020":{"item1":"123","item2":"321","item3":"987",},"30/06/2020":{"item1":"123","item2":"321","item3":"987",},}}})