为数据库Librarymanage中的Bookinfo表创建触发器“tri_Bookdeleted”。执行DELETE操作时，触发器会显示“被删除图书总本数”和“被删除图书价格”

以下是创建触发器 tri_Bookdeleted 的 SQL 语句：

CREATE TRIGGER tri_Bookdeleted
AFTER DELETE ON Bookinfo
FOR EACH ROW
BEGIN
  DECLARE deleted_count INT;
  DECLARE deleted_price FLOAT;
  
  SELECT SUM(amount) INTO deleted_count FROM Bookinfo WHERE BookID = OLD.BookID;
  SELECT SUM(price) INTO deleted_price FROM Bookinfo WHERE BookID = OLD.BookID;
  
  IF deleted_count IS NULL THEN
    SET deleted_count = 0;
  END IF;
  
  IF deleted_price IS NULL THEN
    SET deleted_price = 0;
  END IF;
  
  SELECT CONCAT('被删除图书总本数：', deleted_count, '，被删除图书价格：', deleted_price) AS 'Delete Info';
END

这个触发器会在执行 DELETE 操作后自动触发，计算被删除图书的总本数和价格，并将结果显示出来。触发器使用了两个 SELECT 语句来计算总本数和总价格，然后使用 IF 语句检查结果是否为 NULL，并在必要时将其设置为 0。最后，触发器使用 CONCAT 函数将结果连接成一个字符串，并将其显示出来。