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Asked: 2026-05-18T08:41:53+00:00

Basically, I have a table with all the bus stops of a route with

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Basically, I have a table with all the bus stops of a route with the time_from_start value, that helps to put them in a good order.

CREATE TABLE `api_routestop` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `route_id` int(11) NOT NULL,
  `station_id` varchar(10) NOT NULL,
  `time_from_start` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `api_routestop_4fe3422a` (`route_id`),
  KEY `api_routestop_15e3331d` (`station_id`)
)

I want to return for each stop of a line the time to go to the next stop.

I tried with this QUERY :

SELECT r1.station_id, r2.station_id, r1.route_id, COUNT(*), (r2.time_from_start - r1.time_from_start) as time
FROM api_routestop r1
LEFT JOIN api_routestop r2 ON r1.route_id = r2.route_id AND r1.id <> r2.id
GROUP BY r1.station_id
HAVING time >= 0
ORDER BY r1.route_id, r1.time_from_start, r2.time_from_start

But the group by seams not to work and the result looks like :

+------------+------------+----------+----------+------+
| station_id | station_id | route_id | COUNT(*) | time |
+------------+------------+----------+----------+------+
| Rub01      | Sal01      |        1 |       16 |    1 |
| Lyc02      | Sch02      |        2 |       17 |    2 |
| Paq01      | PoB01      |        3 |       15 |    1 |
| LaT02      | Gco02      |        4 |       16 |    1 |
| Sup01      | Tur01      |        5 |      132 |    1 |
| Oeu02      | CtC02      |        6 |       20 |    2 |
| Ver02      | Elo02      |        7 |       38 |    1 |
| Can01      | Mbo01      |        8 |       70 |    1 |
| Ver01      | Elo01      |        9 |       77 |    1 |
| MCH01      | for02      |       10 |       77 |    1 |
+------------+------------+----------+----------+------+

If I do that : 

SELECT r1.station_id, r2.station_id, r1.route_id, COUNT(*), (r2.time_from_start - r1.time_from_start) as time
FROM api_routestop r1
LEFT JOIN api_routestop r2 ON r1.route_id = r2.route_id AND r1.id <> r2.id
GROUP BY r1.station_id, r2.station_id, r1.route_id
HAVING time >= 0
ORDER BY r1.route_id, r1.time_from_start, r2.time_from_start

I am approching :

+------------+------------+----------+----------+------+
| station_id | station_id | route_id | COUNT(*) | time |
+------------+------------+----------+----------+------+
| Rub01      | Sal01      |        1 |        1 |    1 |
| Rub01      | ARM01      |        1 |        1 |    2 |
| Rub01      | MaV01      |        1 |        1 |    4 |
| Rub01      | COl01      |        1 |        1 |    5 |
| Rub01      | Str01      |        1 |        1 |    6 |
| Rub01      | Jau01      |        1 |        1 |    7 |
| Rub01      | Cdp01      |        1 |        1 |    9 |
| Rub01      | Rep01      |        1 |        1 |   11 |
| Rub01      | CoT01      |        1 |        1 |   12 |
| Rub01      | Ctr01      |        1 |        1 |   14 |
| Rub01      | FLy01      |        1 |        1 |   15 |
| Rub01      | Lib01      |        1 |        1 |   17 |
| Rub01      | Bru01      |        1 |        1 |   18 |
| Rub01      | Sch01      |        1 |        1 |   20 |
| Rub01      | Lyc01      |        1 |        1 |   22 |
| Rub01      | Res01      |        1 |        1 |   24 |
| Sal01      | ARM01      |        1 |        1 |    1 |
| Sal01      | MaV01      |        1 |        1 |    3 |
| Sal01      | COl01      |        1 |        1 |    4 |
| Sal01      | Str01      |        1 |        1 |    5 |
| Sal01      | Jau01      |        1 |        1 |    6 |
| Sal01      | Cdp01      |        1 |        1 |    8 |
| Sal01      | Rep01      |        1 |        1 |   10 |
| Sal01      | CoT01      |        1 |        1 |   11 |
| Sal01      | Ctr01      |        1 |        1 |   13 |
| Sal01      | FLy01      |        1 |        1 |   14 |
| Sal01      | Lib01      |        1 |        1 |   16 |
| Sal01      | Bru01      |        1 |        1 |   17 |
| Sal01      | Sch01      |        1 |        1 |   19 |
| Sal01      | Lyc01      |        1 |        1 |   21 |
...
3769 rows in set (0.07 sec)

But what do I have to do to have only the first result for the same r1.station_id and r1.route_id ?

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1 Answer

  1. Editorial Team

    You’re getting a lot of results back because your getting every stop joined to every other stop on the same route.

    So you’ll need to identify the “Next” stop as the stop that has the same route ID but has a minimum time from start later than the current one

    Update Added routeId to the next_stop sub query to deal with the case of stations used in multiple routes

    SELECT
    r1.station_id, 
    r2.station_id, 
    r1.route_id, 
    r2.time_from_start - r1.time_from_start as time

FROM
api_routestop r1 
INNER JOIN (SELECT 
         r1.station_id , r2.route_id, min(r2.time_from_start) next_time_from_start
FROM 
  api_routestop r1
  LEFT JOIN api_routestop r2 ON r1.route_id = r2.route_id AND r1.id <> r2.id
       and r2.time_from_start > r1.time_from_start
  GROUP BY r1.Station_id, r2.route_id) next_stop

ON r1.Station_id = next_stop.station_id
   and r1.route_id = next_stop.route_id
LEFT JOIN api_routestop r2 
ON r2.time_from_start = r2.next_time_from_start
    and r1.route_id = r2.route_id
AND r2.time_from_start > r1.time_from_start
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