Mysql query joining data from several tables

Question

The db has 4 tables, below is each table definition with some sample data.

stop times(this represents a particular 'stop' for a bus along a route on a particular trip)

trip_id  arrival_time  departure_time  stop_id       stop_sequence
1        06:54:00      06:54:00        9400ZZMAABM1  0001
1        06:56:00      06:56:00        9400ZZMACRU1  0002
1        06:58:00      06:58:00        9400ZZMABOW1  0003
1        07:00:00      07:00:00        9400ZZMAHEA1  0004
1        07:02:00      07:02:00        9400ZZMAPWC1  0005

routes(this represents a route)

route_id      route_short_name   route_long_name
MET:MET2:I:   42                 ALTRINCHAM - MANCHESTER - BURY
MET:MET2:O:   42                 BURY - MANCHESTER - ALTRINCHAM

trips(this represents a particular bus trip)

route_id      trip_id   trip_headsign
MET:MET2:I:   1         "Bury To Manchester"
MET:MET2:I:   2         "Manchester To Bury"

stops(this represents a bus stop)

stop_id      stop_code   stop_name
0600MA0001   chegptg     "Broken Cross, Fallibroome Road (cnr)"
0600MA0050   chegtjm     "Macclesfield, opp Tesco"
0600MA0166   chemjat     "Knutsford, Sugar Pit Lane (cnr)"

I want to get all the stops for a given route. To do this is seems I must join the data from the routes, trips, stops and stop times but I cant get it right. Here is the query I tried:

SELECT 
    routes.route_id,
    routes.route_short_name,
    trips.trip_id,
    stops.stop_id,
    stops.stop_name
FROM routes 
     INNER JOIN trips ON routes.route_id=trips.route_id 
     INNER JOIN stops ON stop_times.stop_id=stops.stop_id
WHERE routes.route_short_name='42';

Answer 1

Your joins use stop_times , but this is not in the from clause. You need all four tables:

SELECT r.route_id, r.route_short_name, t.trip_id, s.stop_id, s.stop_name
FROM routes r INNER JOIN
     trips t
     ON r.route_id = t.route_id INNER JOIN
     stop_times st
     ON st.trip_id = t.trip_id INNER JOIN
     stops s
     on st.stop_id = s.stop_id
WHERE r.route_short_name='42';

Answer 2

I believe this will work for you

SELECT 
    DISTINCT(s.stop_id),
    s.stop_name,
    r.route_short_name
FROM stops s 
     INNER JOIN stop_times st ON st.stop_id = s.stop_id
     INNER JOIN trips t ON t.trip_id = st.trip_id
     INNER JOIN routes r ON r.route_id=t.route_id 
WHERE r.route_short_name='42'
GROUP BY s.stop_id;

you were trying to join a table from a different tables id which doesn't work. you first have to join stop_times to trips and then join stops to stop_times so that your id's match up and you have the stops per corresponding trip.