Sort Data in Parse on basis of pointer array

This is regarding MongoDB, Parse Framework, Android / iOS work. I have two classes(tables) "Group" & "Event". One group can have zero or more events, so in Group table I have stored events in one column as array of pointer . Event has column where we mention the start date of the event. Now I want to list all Groups such that 1) group which has nearest event should be listed on the top while with zero events as last 2) I also have to show events list along with respective group, they should also be sorted chronologically as per start date i.e nearest event first and then later on as per date. Here I tried sorting Events by start date then using whereMatchesQuery function while querying Group table but this doesn't return me groups with zero events , also groups doesn't get sorted such that the group with nearest event is shown at top.