1. 归还图书

   CREATE TRIGGER reserve_book
   AFTER INSERT ON reserve_list
   FOR EACH ROW
   BEGIN
       DECLARE book_stat INT;
       SELECT status INTO book_stat FROM book_info WHERE book_id = NEW.book_id;
   
       UPDATE reader_card SET reserve_time = reserve_time + 1 WHERE reader_id = NEW.reader_id;
   
       IF book_stat = 0 THEN
           UPDATE book_info SET status = 2 WHERE book_id = NEW.book_id;
       END IF;
   END;
   
   

2. 在预约情况下借阅图书

   CREATE TRIGGER take_book
   AFTER UPDATE ON reserve_list
   FOR EACH ROW
   BEGIN
       DECLARE is_reserved INT;
       SELECT COUNT(*) INTO is_reserved FROM reserve_list WHERE book_id = OLD.book_id;
       IF is_reserved = 0 THEN
           UPDATE book_info SET status = 0 WHERE book_id = NEW.book_id;
       ELSE 
           UPDATE book_info SET status = 2 WHERE book_id = NEW.book_id;
       END IF;
   END;
   

3. 删除图书

   CREATE TRIGGER BookDelete
   AFTER DELETE ON book_info
   FOR EACH ROW
   BEGIN
       DELETE FROM reserve_list where book_id = OLD.book_id;
       DELETE FROM lend_list where book_id = OLD.book_id;
   END;
   

MVC三层架构

文件树

└─demo
    ├─src
    │  └─main
    │      └─webapp
    │          ├─img
    │          ├─library
    │          │  ├─bean
    │          │  ├─controller
    │          │  ├─dao
    │          │  └─service
    │          └─WEB-INF
    │              └─jsp

网页代码

用于接收用户提交请求的代码。

处理业务逻辑

直接与数据库交互

删除，编辑，预约

All by 毛陈诚