Firebase, query with “a child exists” as a condition?

Question

I have a database like this (photo attached): Trip has BIDS, and awardedBid. I use awardedBid!=null as a way to determine the trip is sti

Answer 1

You can remove your attribute bidDone and using startAt() to get all the child having awardedBid not null:

ref.orderByChild("awardedBid").startAt("")

or this to get only the child without bid

ref.orderByChild("awardedBid").endAt(null)