Question

I have an Oracle database with a table "Trains".

Each train got a JourneyID and a departureDate as foreign keys (references Journey).

A Journey is a regular trip that a train do on a regular basis (each day, only in the week, only week-ends, special period for vacations, etc...). A journey got a date of departure and a date of arrival. It also contains the dates of the period (begin and end) and a periodicity rule (a varchar, like "everyday" "every week-end", "each day of the week").

I would like to create a trigger that insert a new train, associated to the right journey, for each day in the period, depending of what the period's rule says.

I have a few problems :

How can i write such a trigger ? The trigger will... trigger once per statement, so there is no risk of triggering because of the trigger, right ?

How can i test the periode attributes where my journey foreign key match the period primary key ?

How can i do a "for each day between" with a set of date ? How to handle gaps in the days (like "not week-end" or "only week-end" conditions).

Is it only possible to do such a manipulation with SQL ?? (i assume that yes, but with a lot of subqueries inside the trigger).

Here is my try for each day in the interval :

CREATE TRIGGER Auto_Creation_Trains
BEFORE INSERT OR UPDATE ON Trajets
FOR EACH ROW
BEGIN
  IF type = "Regulier - Taille Normale"
  THEN
    CREATE SEQUENCE temp MINVALUE 1 START WITH 1 INCREMENT BY 1 MAX VALUE 366
    WHILE (temp != fin_periode - debut_periode)
    LOOP
      temp.nextval
      INSERT INTO (trainID,Sits1,Available1,Sits1,Available2,journeyID, depart) TrainInfo(IDTrain.next, 150,150,647,647,:NEW.journeyID);
    END LOOP;
    DROP SEQUENCE temp
  END IF;
END;

Does it seems legit ?

Answer 1

我认为这个想法应该有效，当这个表获得新记录时，将许多记录插入另一个表的想法。但你放在这里的代码是有争议的。

我觉得在这里使用序列不是必需的，只需要一个for循环就可以了。
应该是：

INSERT INTO traininfo（trainID，Sits1，Available1，Sits1，Available2，journeyID，depart）值（IDTrain.next，150,150,647,647，：NEW.journeyID）
除非这只是一个草稿而你的真实插入语句不同，否则我不明白为什么你需要在traininfo表中插入365个相同的记录。

Complicated trigger insert rows depending of value in other table

1 个答案: