Show the manager name for all gas stations.
select manager_name from gas_station
For each of them, also count the number of gas stations opened after 2000.
select manager_name, count(*) from gas_station where open_year > 2000 group by manager_name
Show the results in the descending order of their count.
select manager_name, count(*) from gas_station where open_year > 2000 group by manager_name order by count(*) desc
Which manager name has the most?
select manager_name from gas_station where open_year > 2000 group by manager_name order by count(*) desc limit 1