MySQL操作

USE db_book;
SELECT * FROM v1;
DELETE FROM t_book WHERE id>4;-- 数据太多删掉
-- 第五节:修改视图
-- 5.1 CREATE OR REPLACE VIEW 语句修改视图
-- 格式:
--     CREATE OR REPLACE [ ALGORITHM ={ UNDEFINED | MERGE | TEMPTABLE }]
--     VIEW 视图名 [( 属性清单 )]
--     AS SELECT 语句
--     [ WITH [ CASCADED | LOCAL ] CHECK OPTION ];
SELECT * FROM v1;
CREATE OR REPLACE VIEW v1(书名,价格) AS SELECT bookName,price FROM t_book;
SELECT * FROM v1;

-- 5.2 ALTER 语句修改视图
-- 格式:
--     ALTER [ ALGORITHM ={ UNDEFINED | MERGE | TEMPTABLE }]
--     VIEW 视图名 [( 属性清单 )]
--     AS SELECT 语句
--     [ WITH [ CASCADED | LOCAL ] CHECK OPTION ];
SELECT * FROM v1;
ALTER VIEW v1 AS SELECT * FROM t_book;
SELECT * FROM v1;

-- 第六节:更行视图
--     更新视图是指通过视图来插入（INSERT）、更新（UPDATE）和删除（DELETE）表中的数据。因为视图是一个虚
--     拟的表，其中没有数据。通过视图更新时，都是转换基本表来更新。更新视图时，只能更新权限范围内的数据。
--     超出了范围，就不能更新。
--     6.1 插入(INSERT)
INSERT INTO v1 VALUES(NULL,"第一行代码",79,"郭霖",1);
SELECT * FROM v1;
SELECT * FROM t_book;

--     6.2 更新(UPDATE)
UPDATE v1 SET bookName="第一行代码Android第二版" WHERE bookName="第一行代码";
SELECT * FROM v1;
SELECT * FROM t_book;

--     6.3 删除(DELETE)
INSERT INTO v1 VALUES(NULL,"测试图书01",79,"作者01",3);
INSERT INTO v1 VALUES(NULL,"测试图书02",100,"作者02",2);
SELECT * FROM v1;
SELECT * FROM t_book;

DELETE FROM v1 WHERE id=6;
DELETE FROM v1 WHERE bookName="测试图书02";

SELECT * FROM v1;
SELECT * FROM t_book;

-- 第七节:删除视图
-- 删除视图是指删除数据库中已存在的视图。删除视图时，只能删除视图的定义，不会删除数据；
-- 格式:
--     DROP VIEW [ IF EXISTS ] 视图名列表 [ RESTRICT | CASCADE ]
DROP VIEW IF EXISTS v1;