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ALTER TABLE允许你修改一个现有表的结构。例如，你可以增加或删除列、创造或消去索引、改变现有列的类型、或重新命名列或表本身。你也能改变表的注释和表的类型,当然也可以修改视图了。下面看个实例。ALTER VIEW语法 ALTER [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}] VIEW view_name [(column_list)] AS select_statement [WITH [CASCADED | LOCAL] CHECK OPTION]该语句用于更改已有视图的定义。其语法与CREATE VIEW类似mysql教程>mysql> CREATE TABLE Employee( -> id int, -> first_name VARCHAR(15), -> last_name VARCHAR(15), -> start_date DATE, -> end_date DATE, -> salary FLOAT(8,2), -> city VARCHAR(10), -> description VARCHAR(15) -> );Query OK, 0 rows affected (0.02 sec)mysql>mysql>mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description) -> values (1,'Jason', 'Martin', '19960725', '20060725', 1234.56, 'Toronto', 'Programmer');Query OK, 1 row affected (0.00 sec)mysql>mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description) -> values(2,'Alison', 'Mathews', '19760321', '19860221', 6661.78, 'Vancouver','Tester');Query OK, 1 row affected (0.00 sec)mysql>mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description) -> values(3,'James', 'Smith', '19781212', '19900315', 6544.78, 'Vancouver','Tester');Query OK, 1 row affected (0.00 sec)mysql>mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description) -> values(4,'Celia', 'Rice', '19821024', '19990421', 2344.78, 'Vancouver','Manager');Query OK, 1 row affected (0.00 sec)mysql>mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description) -> values(5,'Robert', 'Black', '19840115', '19980808', 2334.78, 'Vancouver','Tester');Query OK, 1 row affected (0.00 sec)mysql>mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description) -> values(6,'Linda', 'Green', '19870730', '19960104', 4322.78,'New York', 'Tester');Query OK, 1 row affected (0.02 sec)mysql>mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description) -> values(7,'David', 'Larry', '19901231', '19980212', 7897.78,'New York', 'Manager');Query OK, 1 row affected (0.00 sec)mysql>mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description) -> values(8,'James', 'Cat', '19960917', '20020415', 1232.78,'Vancouver', 'Tester');Query OK, 1 row affected (0.00 sec)mysql>mysql> select * from Employee;+------+------------+-----------+------------+------------+---------+-----------+-------------+| id | first_name | last_name | start_date | end_date | salary | city | description |+------+------------+-----------+------------+------------+---------+-----------+-------------+| 1 | Jason | Martin | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto | Programmer || 2 | Alison | Mathews | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester || 3 | James | Smith | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester || 4 | Celia | Rice | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager || 5 | Robert | Black | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester || 6 | Linda | Green | 1987-07-30 | 1996-01-04 | 4322.78 | New York | Tester || 7 | David | Larry | 1990-12-31 | 1998-02-12 | 7897.78 | New York | Manager || 8 | James | Cat | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester |+------+------------+-----------+------------+------------+---------+-----------+-------------+8 rows in set (0.00 sec)mysql>mysql>mysql>mysql> Create VIEW myView (id,first_name,city) -> AS SELECT id, first_name, city FROM employee;Query OK, 0 rows affected (0.00 sec)mysql>mysql> select * from myView;+------+------------+-----------+| id | first_name | city |+------+------------+-----------+| 1 | Jason | Toronto || 2 | Alison | Vancouver || 3 | James | Vancouver || 4 | Celia | Vancouver || 5 | Robert | Vancouver || 6 | Linda | New York || 7 | David | New York || 8 | James | Vancouver |+------+------------+-----------+8 rows in set (0.00 sec)mysql>mysql>mysql> ALTER VIEW myView (id,first_name,city) -> AS SELECT id, upper(first_name), city FROM employee;Query OK, 0 rows affected (0.00 sec)mysql>mysql> select * from myView;+------+------------+-----------+| id | first_name | city |+------+------------+-----------+| 1 | JASON | Toronto || 2 | ALISON | Vancouver || 3 | JAMES | Vancouver || 4 | CELIA | Vancouver || 5 | ROBERT | Vancouver || 6 | LINDA | New York || 7 | DAVID | New York || 8 | JAMES | Vancouver |+------+------------+-----------+8 rows in set (0.02 sec)mysql>mysql> drop view myView;Query OK, 0 rows affected (0.00 sec)mysql>mysql>mysql>mysql>mysql>mysql> drop table Employee;Query OK, 0 rows affected (0.00 sec)mysql> |
