SQL 多表连接一对多关系答案

【问题标题】：SQL Multiple Tables join one to many relationshipSQL 多表连接一对多关系
【发布时间】：2014-01-03 00:48:43
【问题描述】：

您好，我有 3 张桌子，例如

1) 餐桌路线

route_id
route_name
total_stop

2) 餐桌停靠点

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，我在这里做错了什么。请帮忙....

编辑：表结构+数据，SQL FILE

【问题讨论】：

不确定这是答案还是错字，但在您的子查询中您引用了routes.total_stop，而您使用名为total_stops（复数）的列定义了表。
另外，您能否提供每个表中的数据样本以及您当前获得的输出。
stops.stop_latitude 或stops.stop_longitude 是否包含NULL？
@aaroncatlin 我的错误，我已经编辑了
考虑提供适当的 DDL 和/或 sqlfiddle 以及所需的结果集

标签： mysql sql join

【解决方案1】：

请试试这个查询

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)

【讨论】：

【解决方案2】：

你能试试这个查询吗：

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

【讨论】：