[英]SQL Multiple Tables join one to many relationship
嗨我有3张桌子
1)表路线
route_id
route_name
total_stop
2)表停止
stop_id
stop_name
stop_address
stop_latitude
stop_longitude
3)表route_stop
route_id
stop_id
stop_position
我的查询是
SELECT
routes.route_name,
(SELECT
CONCAT(
stops.stop_latitude,
",",
stops.stop_longitude
)
FROM
stops
WHERE stops.stop_id = route_stop.stop_id
AND route_stop.stop_position = 1) AS start_pt,
(SELECT
CONCAT(
stops.stop_latitude,
",",
stops.stop_longitude
)
FROM
stops
WHERE stops.stop_id = route_stop.stop_id
AND route_stop.stop_position = routes.total_stop) AS end_pt,
routes.total_stop
FROM
routes
INNER JOIN route_stop
ON routes.route_id = route_stop.route_id
INNER JOIN stops
ON route_stop.stop_id = stops.stop_id
GROUP BY routes.route_id ;
这里end_pt
列返回NULL,这里我做错了什么。 请帮忙....
编辑:表结构+数据, SQL文件
请尝试此查询
SELECT routes.route_name,
CONCAT(startstop.stop_latitude,",",startstop.stop_longitude) as start_pt,
CONCAT(endstop.stop_latitude,",",endstop.stop_longitude) as end_pt,
routes.total_stop
FROM routes
INNER JOIN route_stop as routestart ON (routestart.route_id=routes.route_id AND routestart.stop_position = 1)
INNER JOIN route_stop as routeend ON (routeend.route_id=routes.route_id AND routeend.stop_position = routes.total_stop)
INNER JOIN stops as startstop ON (startstop.stop_id=routestart.stop_id)
INNER JOIN stops as endstop ON (endstop.stop_id=routeend.stop_id)
你能试试这个问题:
SELECT routes.route_id,routes.route_name, starts.start_pt, ends.end_pt, routes.total_stop
FROM routes
JOIN route_stop ON routes.route_id = route_stop.route_id
JOIN (
SELECT stops.stop_id,CONCAT(stops.stop_latitude,",",stops.stop_longitude) as start_pt
FROM stops
JOIN route_stop ON stops.stop_id = route_stop.stop_id
WHERE route_stop.stop_position = 1
) as starts ON starts.stop_id = route_stop.stop_id
JOIN (
SELECT stops.stop_id,CONCAT(stops.stop_latitude,",",stops.stop_longitude) as end_pt
FROM stops
JOIN route_stop ON stops.stop_id = route_stop.stop_id
JOIN routes ON routes.route_id = route_stop.route_id
WHERE route_stop.stop_position = routes.total_stops
) as ends ON ends.stop_id = route_stop.stop_id
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