mysql:视图

/*样例表*/

CREATE TABLE student

(

  s_id  INT,

  name  VARCHAR(40)

);

CREATE TABLE stu_info

(

  s_id   INT,

  glass  VARCHAR(40),

  addr   VARCHAR(90)

);

【例11.1】在t表格上创建一个名为view_t的视图，代码如下：

CREATE TABLE t (qty INT, price INT);         /*创建基本表t*/

INSERT INTO t VALUES(3, 50);                 /*插入记录*/

CREATE VIEW view_t AS SELECT quantity, price, quantity *price FROM t;    /*创建视图view_t*/

SELECT * FROM view_t;

【例11.2】在t表格上创建一个名为view_t2的视图，代码如下：

CREATE VIEW view_t2(qty, price, total ) AS SELECT quantity, price, quantity *price FROM t;

SELECT * FROM view_t2;

【例11.3】在表student和表stu_info上创建视图stu_glass，代码如下：

INSERT INTO student VALUES(1,'wanglin1'),(2,'gaoli'),(3,'zhanghai');                /*插入记录*/

INSERT INTO stu_info VALUES(1, 'wuban','henan'),(2,'liuban','hebei'),(3,'qiban','shandong');

CREATE VIEW stu_glass (id,name, glass) AS SELECT student.s_id,student.name ,stu_info.glass FROM student ,stu_info WHERE student.s_id=stu_info.s_id;

SELECT * FROM stu_glass;

【例11.4】通过DESCRIBE语句查看视图view_t的定义，代码如下：

DESCRIBE view_t;

【例11.5】下面将通过一个例子来学习使用SHOW TABLE STATUS命令查看视图信息，代码如下：

SHOW TABLE STATUS LIKE 'view_t' \G;

SHOW TABLE STATUS LIKE 't' \G;

【例11.6】SHOW CREATE VIEW查看视图的详细定义，代码如下：

SHOW CREATE VIEW view_t \G;

【例11.7】在views表中查看视图的详细定义，代码如下：

SELECT * FROM information_schema.views \G;

【例11.8】修改视图view_t，代码如下：

DESC view_t;

CREATE OR REPLACE VIEW view_t AS SELECT * FROM t;

DESC view_t;

【例11.9】使用ALTER语句修改视图view_t，代码如下：

DESC view_t;

ALTER VIEW view_t AS SELECT quantity FROM t; 

DESC view_t;

【例11.10】使用UPDATE语句更新视图view_t，代码如下：

SELECT * FROM view_t;          /*查看更新之前的视图*/

SELECT * FROM t;               /*查看更新之前的表*/

UPDATE view_t SET quantity=5;  /*更新视图*/

SELECT * FROM t;               /*查看更新之后的表*/

SELECT * FROM view_t;          /*查看更新之后的视图*/

SELECT * FROM view_t2;

【例11.11】使用INSERT语句在基本表t中插入一条记录，代码如下：

INSERT INTO t VALUES (3,5);

SELECT * FROM t;

SELECT * FROM view_t2;

【例11.12】删除stu_glass视图，代码如下：

DROP VIEW IF EXISTS stu_glass;

SHOW CREATE VIEW stu_glass;