mysql-函数，视图，触发器

存储过程函数

-- 设置数据库的结束符为 ///
mysql> delimiter ///
-- 创建过程函数test
mysql> create procedure test(a int)
    -> begin
    -> select * from student where id=a;
    -> end
    -> ///
Query OK, 0 rows affected (0.01 sec)

mysql> delimiter ;

--调用函数 test
mysql> call test(2);
+----+------+-----+-----+
| id | name | age | sex |
+----+------+-----+-----+
|  2 | lisi |  31 | 0   |
+----+------+-----+-----+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

-- 查看函数 test 的状态信息
mysql> show procedure status like 'test' \G       
*************************** 1. row ***************************
                  Db: shop
                Name: test
                Type: PROCEDURE
             Definer: root@localhost
            Modified: 2018-04-24 12:42:43
             Created: 2018-04-24 12:42:43
       Security_type: DEFINER
             Comment: 
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: utf8_general_ci
1 row in set (0.00 sec)

-- 删除函数 test
mysql> drop procedure test;  

视图

-- 创建视图
mysql> create view test_view(name,age) as select name,age from student where id =5;
Query OK, 0 rows affected (0.00 sec)

-- 视图调用 
mysql> select * from test_view;
+--------+-----+
| name   | age |
+--------+-----+
| tianqi |  42 |
+--------+-----+
1 row in set (0.01 sec)

-- 查看视图的创建过程
mysql> show create view test_view \G

-- 删除视图
mysql> drop view test_view;

触发器

-- artcle表结构，article表开始是空的
mysql> desc article;
+-------+------------------+------+-----+---------+----------------+
| Field | Type             | Null | Key | Default | Extra          |
+-------+------------------+------+-----+---------+----------------+
| id    | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| title | varchar(20)      | NO   |     | NULL    |                |
+-------+------------------+------+-----+---------+----------------+

mysql> desc total_num;
+-------+---------------------+------+-----+---------+----------------+
| Field | Type                | Null | Key | Default | Extra          |
+-------+---------------------+------+-----+---------+----------------+
| id    | int(10) unsigned    | NO   | PRI | NULL    | auto_increment |
| type  | tinyint(3) unsigned | NO   |     | NULL    |                |
| num   | int(10) unsigned    | NO   |     | NULL    |                |
+-------+---------------------+------+-----+---------+----------------+


-- type=1代表文章数  type=2代表用户的数量
mysql> select * from total_num;   
+----+------+-----+
| id | type | num |
+----+------+-----+
|  1 |    1 |   0 |
|  2 |    2 |   0 |
+----+------+-----+

创建触发器，向article表中每增加一条记录，total_num表中的type=1对应num值就加1
mysql> delimiter //
mysql> create trigger add_total_num after insert on article for each row
    -> begin
    -> update total_num set num=num+1 where type=1;
    -> end
    -> //

创建触发器，向article表中每删除一条记录，total_num表中的type=1对应num值就减1
mysql> create trigger delete_total_num after delete on article for each row
    -> begin
    -> update total_num set num=num-1 where type=1;
    -> end
    -> //
		
向article表中插入2条数据，再查看total_num表中的变化
mysql> insert into article(title)values('title1'),('title2');
    -> //

向article表中删除一条记录时，查看total_num表中的变化
mysql> delete from article where id=1;
    -> //

触发器语法

create trigger trigger_name after|before insert|update|delete on table_name for each row begin sql语句 end;