（5） 创建视图

给出一个创建视图的例子：

注意：下边例子红色字体部分为MYSQL数据库取前n条记录的方法，不同于其他数据库。

mysql> select count(*) from test;
+----------+
| count(*) |
+----------+
|     2001 |
+----------+
1 row in set (0.01 sec)

mysql> create view v_test as select * from test limit 20;
Query OK, 0 rows affected (0.06 sec)

mysql> select * from v_test;
+------+------+---------------------+---------------------+
| ID   | MC   | DT                  | RQ                  |
+------+------+---------------------+---------------------+
| 1000 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  999 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  998 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  997 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  996 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  995 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  994 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  993 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  992 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  991 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  990 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  989 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  988 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  987 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  986 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  985 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  984 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  983 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  982 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
|  981 | test | 0000-00-00 00:00:00 | 0000-00-00 00:00:00 |
+------+------+---------------------+---------------------+
20 rows in set (0.06 sec)

和显示函数内容类似，我们也可以按照如下方法获得创建视图的语法内容：

mysql> show create view v_test;

删除视图

mysql> drop view v_test;
Query OK, 0 rows affected (0.02 sec)

（6） 创建触发器

给出一个简单的创建触发器的例子：

mysql> delimiter //
mysql> create trigger tr_test before insert on test for each row
    -> begin
    -> insert into test1(id,mc) values(new.id,new.mc);
    -> end
    -> //
Query OK, 0 rows affected (0.17 sec)
mysql> delimiter ;

mysql> select count(*) from test1;
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (0.00 sec)

mysql> insert into test (id,mc) values(50000,'trigger_to_test1');
Query OK, 1 row affected (0.19 sec)

mysql> select id,mc from test1;
+-------+------------------+
| id    | mc               |
+-------+------------------+
| 50000 | trigger_to_test1 |
+-------+------------------+
1 row in set (0.00 sec)