复杂SQL查询 - 连接表中的字段总和

Question

SQL Fiddle: http://sqlfiddle.com/#!2/b46ea/2

Current SQL:

SELECT `vehicle_journey`.*,
    ADDTIME(departure, SEC_TO_TIME((1))) AS stopDepartureTime
FROM `vehicle_journey`
INNER JOIN `vehicle_journey_days`
    ON `vehicle_journey_days`.`journey_reference` = `vehicle_journey`.`reference`
INNER JOIN `journey_pattern`
    ON `journey_pattern`.`reference` = `vehicle_journey`.`journey_pattern_reference`
INNER JOIN `journey_pattern_timing_link`
    ON `journey_pattern_timing_link`.`section` = `journey_pattern`.`journey_pattern_section`
WHERE `journey_pattern_timing_link`.`stop` = '1900HA030193'
    AND `vehicle_journey_days`.`day` = 'MondayToFriday'

The final aim of this SQL statement is to get the arrival time of a bus based on its departure time in vehicle_journey and the run_time in journey_pattern_timing_link .

The reason this is proving difficult and why I'm asking for help is because of the nature of the journey_pattern_timing_link table. The table is set up to provide the time in seconds it takes to get from one stop to the next (this is so that times are relative to each departure time).

As you will see in the select statement I'm not far from it. The 'ADDTIME' function is where the bus stop's departure time will be calculated. But, you will see a '1' in the value to add to the departure time. This is just a placeholder, essentially it's inside that SEC_TO_TIME function that I need to add up and work out the departure time.

But wait, what are we adding up? Well this is what I meant about the nature of the journey_pattern_timing_link table. What I need to do is get the total of all the run_time fields inside the journey_pattern_timing_link table where the ID is LESS than the one of the selected stop in the where statement AND the journey_pattern_timing_link . section is equal to the one based on the join.

I understand this is a very long question and one that requires a lot of thought but I am well and truly stuck. Looking at the SQL Fiddle's schema browser should help to understand the table structure.

Answer 1

Try this, although SQL fiddle seems to struggle with it:-

SELECT vehicle_journey.id, 
        vehicle_journey.journey_pattern_reference, 
        vehicle_journey.departure, 
        vehicle_journey.service_reference, 
        vehicle_journey.reference, 
        vehicle_journey.code, 
        vehicle_journey_days.day,
        TIME(ADDTIME(departure, SEC_TO_TIME(SUM(jptl2.run_time)))) AS stopDepartureTime
FROM vehicle_journey
INNER JOIN vehicle_journey_days ON vehicle_journey_days.journey_reference = vehicle_journey.reference
INNER JOIN journey_pattern ON journey_pattern.reference = vehicle_journey.journey_pattern_reference
INNER JOIN journey_pattern_timing_link ON journey_pattern_timing_link.section = journey_pattern.journey_pattern_section AND journey_pattern_timing_link.stop = '1900HA080102' 
INNER JOIN journey_pattern_timing_link  jptl2 ON jptl2.section = journey_pattern.journey_pattern_section AND jptl2.ID <= journey_pattern_timing_link.ID
WHERE vehicle_journey_days.day = 'Saturday'
GROUP BY vehicle_journey.id, vehicle_journey.journey_pattern_reference, vehicle_journey.departure, vehicle_journey.service_reference, vehicle_journey.reference, vehicle_journey.code

Answer 2

I think this does it. It does a second join onto journey_pattern_timing_link to get all the stops that are up to and including the stop you are looking for, then sum their run_time and add it to departure :

SELECT 
  `vehicle_journey`.*,
  ADDTIME(departure,SEC_TO_TIME(SUM(`previous_stops`.`run_time`))) `duration`  
FROM `vehicle_journey`
INNER JOIN `vehicle_journey_days`
    ON `vehicle_journey_days`.`journey_reference` = `vehicle_journey`.`reference`
INNER JOIN `journey_pattern`
    ON `journey_pattern`.`reference` = `vehicle_journey`.`journey_pattern_reference`
INNER JOIN `journey_pattern_timing_link`
    ON `journey_pattern_timing_link`.`section` = `journey_pattern`.`journey_pattern_section`
LEFT JOIN `journey_pattern_timing_link` `previous_stops`
    ON `journey_pattern_timing_link`.`section` = `previous_stops`.`section`
    AND `journey_pattern_timing_link`.`id` >= `previous_stops`.`id`
WHERE `journey_pattern_timing_link`.`stop` = '1900HA080987'
    AND `vehicle_journey_days`.`day` = 'Saturday'
GROUP BY
  `vehicle_journey`.`id`,
  `vehicle_journey`.`journey_pattern_reference`,
  `vehicle_journey`.`departure`,
  `vehicle_journey`.`service_reference`,
  `vehicle_journey`.`reference`,
  `vehicle_journey`.`code`