为数据库Librarymanage中的readerinfo表,执行UPDATE操作的触发器,触发器名称为tri_readerupdate,当更新一名读者电话信息时,显示读者姓名、原电话号码和新电话号码。
时间: 2024-02-13 19:07:19 浏览: 27
好的,以下是触发器的代码:
```
CREATE TRIGGER tri_readerupdate
AFTER UPDATE ON readerinfo
FOR EACH ROW
BEGIN
DECLARE reader_name VARCHAR(50);
DECLARE original_phone VARCHAR(20);
DECLARE new_phone VARCHAR(20);
SELECT name INTO reader_name FROM readerinfo WHERE reader_id = NEW.reader_id;
SELECT phone INTO original_phone FROM readerinfo WHERE reader_id = NEW.reader_id;
SET new_phone = NEW.phone;
IF original_phone <> new_phone THEN
SELECT CONCAT("Reader ", reader_name, " phone number has been updated from ", original_phone, " to ", new_phone) AS message;
END IF;
END;
```
当更新一名读者的电话信息时,该触发器会获取该读者的姓名、原电话号码和新电话号码,并判断是否有改变。如果有改变,则会输出一条包含读者姓名、原电话号码和新电话号码的消息。请注意,该触发器是在每次更新readerinfo表的每一行时执行的。