Show the total passengers for all train stations.
select total_passengers from station
Show the total passengers for those in either London or Glasgow.
select total_passengers from station where location = 'London' or location = 'Glasgow'
What is the average?
select avg(total_passengers) from station where location = 'London' or location = 'Glasgow'
Also show the maximum.
select avg(total_passengers), max(total_passengers) from station where location = 'London' or location = 'Glasgow'