MySQL可更新视图

-- 当前环境
mysql> show variables like 'version';
+---------------+--------+
| Variable_name | Value |
+---------------+--------+
| version | 5.7.17 |
+---------------+--------+
-- 可更新视图演示

DROP TABLE IF EXISTS items;

CREATE TABLE items
(
   id INT AUTO_INCREMENT PRIMARY KEY,
   name VARCHAR(100) NOT NULL,
   price DECIMAL(11, 2) NOT NULL
);

-- 为items表填充数据

INSERT INTO items(name, price)
VALUES ('Laptop', 700.56), ('Desktop', 699.99), ('iPad', 700.50);

CREATE OR REPLACE VIEW vw_items
AS
   SELECT *
   FROM items
   WHERE price > 700;

-- 查询视图

SELECT * FROM vw_items;

-- 以下语句插入成功，基表和视图同时可见

INSERT INTO vw_items
VALUES (NULL, 'iPhone', 800.50);

-- 以下语句插入成功，基表可见，因为视图包含了where子句对其过滤

INSERT INTO vw_items
VALUES (NULL, 'iPhone4', 500.50);

-- Query OK, 1 row affected (0.00 sec)

SELECT * FROM vw_items;

-- 先清空一下数据

TRUNCATE TABLE items;

CREATE OR REPLACE VIEW vw_items_check
AS
   SELECT *
   FROM items
   WHERE price > 700
   WITH CHECK OPTION;

-- 下面基于vw_items_check创建另外一个视图vw_items_check2
CREATE OR REPLACE VIEW vw_items_check2
AS
   SELECT *
   FROM vw_items_check
   WHERE price < 1000
   WITH LOCAL CHECK OPTION;

-- 下面基于vw_items_check创建另外一个视图vw_items_check3
CREATE OR REPLACE VIEW vw_items_check3
AS
   SELECT *
   FROM vw_items_check
   WHERE price < 1000
   WITH CASCADED CHECK OPTION;

-- 基于视图vw_items_check插入数据，以下语句插入失败，不符合视图过滤条件
INSERT INTO vw_items_check
VALUES (NULL, 'Laptop', 600.56);

-- ERROR 1369 (HY000): CHECK OPTION failed 'sakila.vw_items_check'

-- 基于视图vw_items_check插入数据，以下语句执行成功
-- 满足where子句过滤条件，插入后基表和视图数据可见
INSERT INTO vw_items_check
VALUES (NULL, 'Laptop', 700.56);

-- 基于视图vw_items_check2插入数据成功，值符合过滤条件
INSERT INTO vw_items_check2
VALUES (NULL, 'iPhone', 800.50);

-- 基于视图vw_items_check3插入数据成功，值符合过滤条件
INSERT INTO vw_items_check3
VALUES (NULL, 'iPhone3', 800.50);

-- 下面使用一个不符合预期的值进行插入
-- 基于视图vw_items_check2插入数据失败，值不符合底层过滤条件
INSERT INTO vw_items_check2
VALUES (NULL, 'iPhone_chk2', 700);

-- ERROR 1369 (HY000): CHECK OPTION failed 'sakila.vw_items_check2'

-- 基于视图vw_items_check3插入数据失败，值不符合底层过滤条件
INSERT INTO vw_items_check3
VALUES (NULL, 'iPhone_chk2', 700);

-- ERROR 1369 (HY000): CHECK OPTION failed 'sakila.vw_items_check3'

-- 通过上面的测试发现，使用CASCADED与LOCAL创建的视图都会检查底层依赖
-- 在此并无特别
-- 说明5.7.6版本以前，视图vw_items_check2不符合底层预期时，也可以成功执行

-- 再次创建如下视图，此时的视图底层基于非check视图

CREATE OR REPLACE VIEW vw_items_check4
AS
   SELECT *
   FROM vw_items
   WHERE price < 1000
   WITH LOCAL CHECK OPTION;

CREATE OR REPLACE VIEW vw_items_check5
AS
   SELECT *
   FROM vw_items
   WHERE price < 1000
   WITH CASCADED CHECK OPTION;

-- 基于视图vw_items_check4插入数据成功，值不符合底层过滤条件
-- 但是此时可以成功插入，说明local生效，不依赖底层过滤条件    
INSERT INTO vw_items_check4
VALUES (NULL, 'iPhone_chk4', 700);    

Query OK, 1 row affected (0.00 sec)

-- 下面验证插入结果，查询vw_items_check4被过滤
SELECT * FROM vw_items_check4;
+----+---------+--------+
| id | name | price |
+----+---------+--------+
| 1 | Laptop | 700.56 |
| 2 | iPhone | 800.50 |
| 3 | iPhone3 | 800.50 |
+----+---------+--------+

-- 查询基表数据存在
SELECT * FROM items;
+----+-------------+--------+
| id | name | price |
+----+-------------+--------+
| 1 | Laptop | 700.56 |
| 2 | iPhone | 800.50 |
| 3 | iPhone3 | 800.50 |
| 4 | iPhone_chk4 | 700.00 |
+----+-------------+--------+

-- 基于视图vw_items_check5插入数据失败，cascade级联校验生效
INSERT INTO vw_items_check5
VALUES (NULL, 'iPhone_chk5', 700);

-- ERROR 1369 (HY000): CHECK OPTION failed 'sakila.vw_items_check5'

-- 基于视图vw_items_check4删除数据
-- 如下，提示删除成功，但基表数据未删除，因为不满足过滤条件
DELETE FROM vw_items_check4
WHERE id = 4;

-- Query OK, 0 rows affected (0.00 sec)

-- Author : Leshami
-- Blog : http://blog.csdn.net/leshami

-- 基于视图vw_items_check5删除数据
-- 如下，提示删除成功，但基表数据未删除，因为不满足过滤条件
DELETE FROM vw_items_check5
WHERE id = 4;

-- Query OK, 0 rows affected (0.00 sec)

-- 满足过滤条件 id为3的记录能够被删除
DELETE FROM vw_items_check5
WHERE id = 3;

-- Query OK, 1 row affected (0.00 sec)

-- 删除后的结果
SELECT * FROM items;
+----+-------------+--------+
| id | name | price |
+----+-------------+--------+
| 1 | Laptop | 700.56 |
| 2 | iPhone | 800.50 |
| 4 | iPhone_chk4 | 700.00 |
+----+-------------+--------+

-- 由于不符合过滤条件，2个视图均无法更新
UPDATE vw_items_check5
SET price = 701
WHERE id = 4;    

Query OK, 0 rows affected (0.00 sec)
Rows matched: 0 Changed: 0 Warnings: 0

UPDATE vw_items_check4
SET price = 701
WHERE id = 4;   

Query OK, 0 rows affected (0.00 sec)
Rows matched: 0 Changed: 0 Warnings: 0

-- 基于视图vw_items5更新数据，此时选择满足条件的记录来更新
-- 更新为比过滤条件低的价格，无法成功更新
UPDATE vw_items_check5
SET price = 700
WHERE id = 2; 

ERROR 1369 (HY000): CHECK OPTION failed 'sakila.vw_items_check5'

-- 更新为符合条件时，被成功更新
UPDATE vw_items_check5
SET price = 900
WHERE id = 2;

Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

-- 未指定local与cascade时，缺省为cascade
-- 官方给出的关于LOCAL与CASCADED对比
/*

• With LOCAL, the view WHERE clause is checked, then checking recurses to underlying views and
applies the same rules.

• With CASCADED, the view WHERE clause is checked, then checking recurses to underlying views,
adds WITH CASCADED CHECK OPTION to them (for purposes of the check; their definitions remain
unchanged), and applies the same rules.

• With no check option, the view WHERE clause is not checked, then checking recurses to underlying
views, and applies the same rules.
*/