1.创建90后读者信息的视图view_after90。

CREATE VIEW view_after90     
AS
 SELECT *	
FROM t_reader 	
WHERE reader_birthday between "1990-1-1" and "1999-12-31";
DESC view_after90;

2.创建“清华大学出版社”出版的图书信息的视图 view_qinghua。

CREATE VIEW view_qinghua 
AS
SELECT a.* from t_book a,t_press b 
WHERE a.press_id=b.press_id 
AND b.press_name='清华大学出版社';

3.修改视图view_after90，改为包含80后读者信息。

ALTER VIEW view_after90 
AS
 SELECT *	
 FROM t_reader 	
 WHERE reader_birthday between "1980-1-1" and "1989-12-31";
SELECT * FROM view_after90;

4.删除视图view_after90。

DROP VIEW IF EXISTS view_after90;
DESC view_after90;