Question

我有三个3个表（类，模块，module_classes），为简单起见，它们如下：班级表：

+-----+---------+----------+-----------+-----------+
| id  |  name   |  level   |  deleted  |create_time|
+-----|---------+----------|-----------+-----------+
|1    | C1      |4         | 1         |some date  |
|2    | C2      |2         | 0         |some date  |
|3    | C1      |1         | 0         |some date  | 
+-----+---------+----------+-----------+-----------+

模块表：

+-----+---------+----------+
| id  |  name   |  deleted |
+-----|---------+----------|
|1    | M1      |0         |
|2    | M2      |0         | 
|3    | M1      |0         |  
+-----+---------+----------+

module_class表：

+-----+---------+----------+
| id  | classId | moduleId |
+-----|---------+----------|
|1    | 1       |1         |
|2    | 2       |2         |
|3    | 1       |3         | 
+-----+---------+----------+

每学期一级增加一级，4学期后该类将被设置为删除，并且将插入具有相同名称但级别为1的新类，模块将保持不变，module_class中的类ID必须为从已删除的更新到插入的类，因此必须如下所示：

+-----+---------+----------+
| id  | classId | moduleId |
+-----|---------+----------|
|1    | 3       |1         |
|2    | 2       |2         |
|3    | 3       |3         | 
+-----+---------+----------+

我无法想象如何使它成为可能，任何关于如何做到这一点的建议？提前谢谢

Answer 1

尝试此触发器

DROP TRIGGER IF EXISTS TRIGGER_class_UPDATE;
DELIMITER $$
CREATE TRIGGER TRIGGER_class_UPDATE BEFORE UPDATE ON class FOR EACH ROW BEGIN
   SET @moduleId= (SELECT moduleId FROM module_class WHERE class_id=old.id);
   IF NEW.level=4 THEN 
      SET NEW.deleted=1;
      INSERT INTO class(name,level,deleted,create_time) values (old.name,1,0,now());
        set @newclassid=(SELECT ID FROM class WHERE name=old.anem and deleted=0 and level=old.level);
       INSERT INTO module_class(classId,moduleId) values (@newclassid,@moduleId);
   ELSE
      SET NEW.deleted=0;
   END IF;
END$$ 
DELIMITER ;

https://dev.mysql.com/doc/refman/5.5/en/trigger-syntax.html

sql：我需要帮助来搞清楚查询

1 个答案: