262. 行程和用户

SELECT request_at as Day, 
ROUND(sum(case when status = 'completed' then 0 else 1 end)/count(*),2) as 'Cancellation rate' 
FROM(
SELECT id,request_at,status
FROM Trips inner join Users U1 on client_id = U1.users_id and U1.banned = 'NO'
inner join Users U2 on driver_id = U2.users_id and U2.banned = 'NO') t
GROUP BY request_at
HAVING request_at BETWEEN '2013-10-01' AND '2013-10-03'