mysql_14_視圖的修改_更新_刪除

USE db_book;
SELECT * FROM v1;
DELETE FROM t_book WHERE id>4;-- 數據太多刪掉
-- 第五節:修改視圖
-- 5.1 CREATE OR REPLACE VIEW 語句修改視圖
-- 格式:
--     CREATE OR REPLACE [ ALGORITHM ={ UNDEFINED | MERGE | TEMPTABLE }]
--     VIEW 視圖名 [( 屬性清單 )]
--     AS SELECT 語句
--     [ WITH [ CASCADED | LOCAL ] CHECK OPTION ];
SELECT * FROM v1;
CREATE OR REPLACE VIEW v1(書名,價格) AS SELECT bookName,price FROM t_book;
SELECT * FROM v1;

-- 5.2 ALTER 語句修改視圖
-- 格式:
--     ALTER [ ALGORITHM ={ UNDEFINED | MERGE | TEMPTABLE }]
--     VIEW 視圖名 [( 屬性清單 )]
--     AS SELECT 語句
--     [ WITH [ CASCADED | LOCAL ] CHECK OPTION ];
SELECT * FROM v1;
ALTER VIEW v1 AS SELECT * FROM t_book;
SELECT * FROM v1;

-- 第六節:更行視圖
--     更新視圖是指通過視圖來插入（INSERT）、更新（UPDATE）和刪除（DELETE）表中的數據。因為視圖是一個虛
--     擬的表，其中沒有數據。通過視圖更新時，都是轉換基本表來更新。更新視圖時，只能更新權限范圍內的數據。
--     超出了范圍，就不能更新。
--     6.1 插入(INSERT)
INSERT INTO v1 VALUES(NULL,"第一行代碼",79,"郭霖",1);
SELECT * FROM v1;
SELECT * FROM t_book;

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

--     6.3 刪除(DELETE)
INSERT INTO v1 VALUES(NULL,"測試圖書01",79,"作者01",3);
INSERT INTO v1 VALUES(NULL,"測試圖書02",100,"作者02",2);
SELECT * FROM v1;
SELECT * FROM t_book;

DELETE FROM v1 WHERE id=6;
DELETE FROM v1 WHERE bookName="測試圖書02";

SELECT * FROM v1;
SELECT * FROM t_book;

-- 第七節:刪除視圖
-- 刪除視圖是指刪除數據庫中已存在的視圖。刪除視圖時，只能刪除視圖的定義，不會刪除數據；
-- 格式:
--     DROP VIEW [ IF EXISTS ] 視圖名列表 [ RESTRICT | CASCADE ]
DROP VIEW IF EXISTS v1;