使用外键填充表

Question

我有这样的架构

CREATE TABLE TrainManager(
    train_name    VARCHAR(5) REFERENCES Train(name),
    station_id      INT REFERENCES Station(station_id)
);

这两个参考表具有间接关系。

  

control（ctrl_id，train_name）;

     

controlremote（ctrl_id，station_id）;

尽可能地为了获得train name和station id，除了比较train_name和station_id之外，我们需要进入另外两个表来比较ctrl_id。

$query = "INSERT INTO `train` (train_name, station_id)
    SELECT t.train_name, st.station_id
    FROM train, station
    WHERE t.train_name = ( SELECT c.train_name FROM control c
                           WHERE c.train_name = t.train_name)
            AND
          st.station_id = ( SELECT cr.station_id FROM controlremote cr
                            WHERE cr.station_id = st.station_id)
            AND

但我想不出一个合适的SQL synatx来比较ctrl_id ......

Answer 1

INSERT INTO `train` (train_name, station_id)
SELECT control.train_name, controlremote.station_id
FROM control
LEFT JOIN controlremote ON control.ctrl_id = controlremote.ctrl_id

这样的事情。只需加入ctrl_id上的两个表格即可。我希望我理解正确。