数据库-mysql视图

　　视图是一个虚拟表（非真实存在），其本质是【根据SQL语句获取动态的数据集，并为其命名】，用户使用时只需使用【名称】即可获取结果集，并可以将其当作表来使用

一：创建视图

　　create view viewname as select tname from table1,table2 where condition

MariaDB [test2]> create view student2 as select * from student;
Query OK, 0 rows affected (0.02 sec)

MariaDB [test2]> show tables;
+-----------------+
| Tables_in_test2 |
+-----------------+
| a               |
| b               |
| student         |
| student2        |
+-----------------+
4 rows in set (0.00 sec)

二：删除视图

　　drop view viewname

MariaDB [test2]> drop view student2;
Query OK, 0 rows affected (0.00 sec)

MariaDB [test2]> show tables;
+-----------------+
| Tables_in_test2 |
+-----------------+
| a               |
| b               |
| student         |
+-----------------+
3 rows in set (0.00 sec)

三：修改视图

　　alter view viewname as select tname from table1,table2 where condition

　　

MariaDB [test2]> alter view student2 as select * from a;
Query OK, 0 rows affected (0.00 sec)