Which station ids ever had bike availability below 7?
select distinct station_id from status group by station_id having min(bikes_available) < 7
Which did not?
select id from station except select station_id from status group by station_id having min(bikes_available) < 7
Force those stations to additionally have latitude above 37.4.
select id from station where lat > 37.4 except select station_id from status group by station_id having min(bikes_available) < 7