DBA04 一、视图的基本使用 二、视图进阶操作 三、创建存储过程 四、存储过程参数的使用 五、使用循环结构

一、视图的基本使用

1）创建视图：
语法格式：
create view 视图名称 as SQL查询;
create view 视图名称（字段名称列表） as SQL查询;
2）查看视图：
查看当前库下所有表的状态信息
show table status;
show table status where ccomment=“view”\G;
查看创建视图具体命令：
show create view 视图名;
例子：
先创建数据库数据的库和表做模版

mysql> create database db9;
mysql>create table user(
	> name char(30),
	> password char(1),
	> uid int,
	> gid int,
	> comment char(150),
	> homedir char(150),
	> shell char(50),
	> index(name));

系统命令system

mysql> system cp /etc/passwd /mydir		//使用系统命令拷贝/etc/passwd到/mydir
mysql> system ls /mydir
mysql> load data infile "/mydir/passwd"
	> into table db9.user
	> fields terminated by ":"
	> lines terminated by "\n";

创建视图：

mysql> creare view u(v_name,v_uid) as select * from user where name="mail" and uid=8;
mysql> select * from u;
+--------+-------+
| v_name | v_uid |
+--------+-------+
| mail   |     8 |
+--------+-------+

3）视图的查询、插入、更新、删除
语法格式：
select 字段名列表 from 视图名 where 条件；
insert into 视图名（字段名列表） values(字段值列表);
update 视图名 set 字段名=值 where 条件；
delete from 视图名 where 条件；
视图即虚拟表与物理表两者可为相互同步，一旦物理表删除则虚拟表无法进行增删改查。
3）删除视图
语法格式：
drop view 视图名;

二、视图进阶操作

设置字段别名：

1）快速创建两张表做练习测试：

mysql> create table user02 select name,uid,gid from user limit 3;			//使用user表前3行快速建user02表
mysql> select * from user02;
+--------+------+------+
| name   | uid  | gid  |
+--------+------+------+
| root   |    0 |    0 |
| bin    |    1 |    1 |
| daemon |    2 |    2 |
+--------+------+------+
mysql> create table user03 select name,uid,homedir,shell from user limit 5;		//使用user表前5行快速建user03表
mysql> select * from user03;
+--------+------+----------------+---------------+
| name   | uid  | homedir        | shell         |
+--------+------+----------------+---------------+
| root   |    0 | /root          | /bin/bash     |
| bin    |    1 | /bin           | /sbin/nologin |
| daemon |    2 | /sbin          | /sbin/nologin |
| adm    |   10 | /var/adm       | /sbin/nologin |
| lp     |    4 | /var/spool/lpd | /sbin/nologin |
+--------+------+----------------+---------------+

查询user02.name=user03.name的字段

mysql> select * from user02 left join user03 on user02.name=user03.name;
+--------+------+------+--------+------+---------+---------------+
| name   | uid  | gid  | name   | uid  | homedir | shell         |
+--------+------+------+--------+------+---------+---------------+
| root   |    0 |    0 | root   |    0 | /root   | /bin/bash     |
| bin    |    1 |    1 | bin    |    1 | /bin    | /sbin/nologin |
| daemon |    2 |    2 | daemon |    2 | /sbin   | /sbin/nologin |
+--------+------+------+--------+------+---------+---------------+

2）关联查询建的视图，默认不允许修改视图字段的值

mysql> create view v01 as select * from user02 left join user03 on user02.name=user03.name;		//创建失败
ERROR 1060 (42S21): Duplicate column name 'name'
//默认不允许修改视图字段的值

3）创建视图时指定字段别名
方法一：
mysql> create view v01(a,b,c,d,e,f,g) as select * from
> user02,user03 where
> user02.name=user03.name and user02.uid=user03.uid;
Query OK, 0 rows affected (0.05 sec)

mysql> select * from v01;
±-------±-----±-----±-------±-----±------±--------------+
| a | b | c | d | e | f | g |
±-------±-----±-----±-------±-----±------±--------------+
| root | 0 | 0 | root | 0 | /root | /bin/bash |
| bin | 1 | 1 | bin | 1 | /bin | /sbin/nologin |
| daemon | 2 | 2 | daemon | 2 | /sbin | /sbin/nologin |
±-------±-----±-----±-------±-----±------±--------------+
方法二：

mysql> select user02.name as a,
    -> user03.name as d,
    -> user03.homedir as f,user03.shell as g from user02,user03
    -> where user02.name=user03.name;
+--------+--------+-------+---------------+
| a      | d      | f     | g             |
+--------+--------+-------+---------------+
| root   | root   | /root | /bin/bash     |
| bin    | bin    | /bin  | /sbin/nologin |
| daemon | daemon | /sbin | /sbin/nologin |
+--------+--------+-------+---------------+

查询时给表起别名：

mysql> create view v02 as select
    -> a.name as aname,b.name as bname,a.uid as auid,
    -> b.uid as buid
    -> from user02 a left join user03 b on a.uid=b.uid;
Query OK, 0 rows affected (0.04 sec)

mysql> select * from v02;
+--------+--------+------+------+
| aname  | bname  | auid | buid |
+--------+--------+------+------+
| root   | root   |    0 |    0 |
| bin    | bin    |    1 |    1 |
| daemon | daemon |    2 |    2 |
+--------+--------+------+------+
3 rows in set (0.00 sec)

 三、创建存储过程

• 存储过程，相当于MySQL语句组成的脚本
  —指的是数据库中保存的一系列SQL命令的集合
  —可以在存储过程中使用变量、条件判断、流程控制等

• 存储过程优点
  提高性能
  可减轻网络负担
  可以防止对表的直接访问
  避免重复编写SQL操作

存储过程的基本使用
1）创建存储过程
语法格式：
mysql> delimiter //
mysql> create procedure 名称()
mysql> begin
mysql> …功能代码
mysql> end
mysql> // //结束存储过程
mysql> Delimiter;

例如：

mysql> delimiter //
mysql> create procedure db9.say()
    -> begin
    -> select name,uid from db9.user where id<=7;
    -> select * from db9.t1;
    -> end
    -> //
Query OK, 0 rows affected (0.03 sec)

mysql> delimiter ;

2）调用
语法格式：
call 存储过程名();

mysql> call db9.say();
+----------+------+
| name     | uid  |
+----------+------+
| root     |    0 |
| bin      |    1 |
| daemon   |    2 |
| adm      |   10 |
| lp       |    4 |
| sync     |    5 |
| shutdown |    6 |
+----------+------+
7 rows in set (0.00 sec)

+--------+------+---------------+
| name   | uid  | shell         |
+--------+------+---------------+
| root   |    0 | /bin/bash     |
| bin    |    1 | /sbin/nologin |
| daemon |    3 | /sbin/nologin |
+--------+------+---------------+
3 rows in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

3）删除
语法格式：
mysql> drop procedure 存储过程名;

mysql> drop procedure say;
Query OK, 0 rows affected (0.00 sec)

mysql> call say;
ERROR 1305 (42000): PROCEDURE db9.say does not exist

4）查看存储过程
方法一：

mysql> show procedure status\G;

方法二：
格式：
mysql> select db,name,type from mysql.proc where name=“存储过程名”;
例如：

mysql> select db,name,type from mysql.proc where name="say";
+-----+------+-----------+
| db  | name | type      |
+-----+------+-----------+
| db9 | say  | PROCEDURE |
+-----+------+-----------+
1 row in set (0.00 sec)

5）查看过程的具体代码

mysql> select db,name,type from mysql.proc
			> where type="PROCEDURE" and name="say";

6）查看有哪些存储过程

mysql> select db,name,type from mysql.proc
		> where type="PROCEDURE" and name="say";

练习：
存储过程名称为p1
功能显示user表中shell 是/bin/bash和/bin/nologin的用户个数
调用存储过程p1

mysql> delimiter //
mysql> create procedure p1()
    -> begin
    -> select count(*) from user where shell="/bin/bash";
    -> select count(*) from user where shell="/bin/nologin";
    -> end
    -> //
Query OK, 0 rows affected (0.00 sec)

mysql> delimiter ;
mysql> call p1;
+----------+
| count(*) |
+----------+
|        2 |
+----------+
1 row in set (0.00 sec)

+----------+
| count(*) |
+----------+

|        0 |
+----------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

三.一、存储过程进阶

1）

mysql> show global variables;					//查看全局变量
mysql> show session variables;				//查看会话变量
mysql> set session sort_buffer_size = 4000;						//设置会话变量
mysql> show session variables like "sort_buffer_size";		//查看会话变量
+------------------+--------+
| Variable_name    | Value  |
+------------------+--------+
| sort_buffer_size | 262144 |
+------------------+--------+
1 row in set (0.00 sec)

mysql> show global variables like "%关键字%";			//查看全局变量
mysql> show global variables like "%host%";
+-------------------------------+----------+
| Variable_name                 | Value    |
+-------------------------------+----------+
| host_cache_size               | 279      |
| hostname                      | mysql155 |
| performance_schema_hosts_size | -1       |
| report_host                   |          |
+-------------------------------+----------+
mysql> set @y=3;			//用户自定义变量，直接赋值
mysql> select @y;
+------+
| @y   |
+------+

|    3 |
+------+

mysql> select max(uid) into @y from user;				//使用SQL命令查询结果赋值,将user表中uid的最大值赋值给自定义变量
mysql> select @y;
+-------+
| @y    |
+-------+
| 65534 |
+-------+

2）参数类型

• 调用参数时，名称前也不需要加@
  –create procedure 名称（
  类型 参数名 数据类型，
  类型 参数名 数据类型
  ）
  begin
  …
  in关键字：

  mysql>  create procedure conf(in a int,in b int)
        ->  begin
        -> declare x int;
        -> declare y int;
        ->  declare z int;
        -> set x = a;
        -> set y = b;
        -> set z = x + y;
        -> select z;
        -> end
        -> //
    Query OK, 0 rows affected (0.00 sec)  
    
    mysql> delimiter ;
    mysql> call conf(10,10);
    +------+
    | z    |
    +------+
    |   20 |
    +------+
    1 row in set (0.00 sec)
  Query OK, 0 rows affected (0.00 sec)
  

out关键字：

mysql> create procedure sy(out x int)
    -> begin
    -> select count(uid) into x from db9.user;
    -> select x;
    -> end
    -> //
Query OK, 0 rows affected (0.00 sec)

mysql> delimiter ;
mysql> select @j;
+------+
| @j   |
+------+
| NULL |
+------+
1 row in set (0.00 sec)

mysql> call sy(@j);
+------+
| x    |
+------+
|   41 |
+------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

mysql> select @j;
+------+

| @j   |
+------+
|   41 |
+------+
1 row in set (0.00 sec)

inout关键字连用：

mysql> delimiter //
mysql> create procedure er(inout x int)
    -> begin
    -> select x;
    -> select count(name) into x from db9.user where shell="/bin/bash";
    -> end
    -> //
Query OK, 0 rows affected (0.00 sec)

mysql> delimiter ;
mysql> select @i;
+------+
| @i   |
+------+
|    2 |
+------+
1 row in set (0.00 sec)

mysql> call er(@i);
+------+
| x    |
+------+
|    2 |
+------+
1 row in set (0.01 sec)

Query OK, 1 row affected (0.01 sec)

mysql> select @i;
+------+
| @i   |
+------+
|    2 |
+------+
1 row in set (0.00 sec)

练习：使用inout指定查看用户

mysql> delimiter //
mysql> create procedure qw(in username varchar(10))
    -> begin
    -> select username;
    -> select * from user where name=username;
    -> end
    -> //
Query OK, 0 rows affected (0.00 sec)

mysql> delimiter ;
mysql> call qw("root");
+----------+
| username |
+----------+
| root     |
+----------+
1 row in set (0.00 sec)

+----+------+----------+------+------+---------+---------+-----------+
| id | name | password | uid  | gid  | comment | homedir | shell     |
+----+------+----------+------+------+---------+---------+-----------+
|  1 | root | x        |    0 |    0 | root    | /root   | /bin/bash |
+----+------+----------+------+------+---------+---------+-----------+
1 row in set (0.00 sec)

3）算数运算

定义局部变量x,y,z要求如下：
—x统计字段shell=/bin/bash的个数
—y统计字段shell=/sbin/nologin的个数
—z统计x,y的总数。

mysql> delimiter //
mysql> create procedure co()
    -> begin
    -> declare x int default 0;
    -> declare y int default 0;
    -> declare z int default 0;
    -> select count(*) into x from db9.user where shell="/bin/bash";
    -> select count(*) into y from db9.user where shell="/sbin/nologin";
    -> set z = x + y;
    -> select z;
    -> end
    -> //
Query OK, 0 rows affected (0.00 sec)

mysql> delimiter ;
mysql> call co;
+------+
| z    |
+------+
|   37 |
+------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

create procedure if not exits … //覆盖创建