MYSQL学习之视图

标签：rows affected 0.00 视图学习 sec MYSQL OK Query

MYSQL学习之视图_视图

（一）什么是视图？？

视图就是站在不同的角度取看待同一份数据。

（二）基本操作

表复制：

mysql>create table dept2 as select * from dept;

#复制
mysql> create table scholar1 as select * from scholor;
Query OK, 3 rows affected (0.02 sec)
Records: 3  Duplicates: 0  Warnings: 0

#查看
mysql> select * from scholar1;
+----+------+
| id | name |
+----+------+
|  1 | 小张 |
|  2 | 小李 |
|  3 | 小明 |
+----+------+
3 rows in set (0.00 sec)

I. 创建视图

mysql> create view scholar1_view as select * from scholar1;
Query OK, 0 rows affected (0.01 sec)

II.删除视图

mysql> drop view scholar1_view;
Query OK, 0 rows affected (0.01 sec)

注意：只有DOL语句才能够以view的形式创建

III.视图的作用

可以面向视图对象进行增删改查，对视图对象的增删改查，会导致原表数据被操作（视图和原表变化一致）

mysql> create view scholar1_view as select * from scholar1;
Query OK, 0 rows affected (0.01 sec)

#面向视图查询
mysql> select * from scholar1_view;
+----+------+
| id | name |
+----+------+
|  1 | 小张 |
|  2 | 小李 |
|  3 | 小明 |
+----+------+
3 rows in set (0.00 sec)
#面向视图插入
mysql> insert into scholar1_view(id,name)values(4,'小红');
Query OK, 1 row affected (0.01 sec)
#面向视图查询
mysql> select * from scholar1_view;
+----+------+
| id | name |
+----+------+
|  1 | 小张 |
|  2 | 小李 |
|  3 | 小明 |
|  4 | 小红 |
+----+------+
4 rows in set (0.00 sec)
#查询原表数据
mysql> select * from scholar1;;
+----+------+
| id | name |
+----+------+
|  1 | 小张 |
|  2 | 小李 |
|  3 | 小明 |
|  4 | 小红 |
+----+------+
4 rows in set (0.00 sec)

#面向视图删除
mysql> delete from scholar1_view;
Query OK, 4 rows affected (0.01 sec)
#面向视图查询
mysql> select * from scholar1_view;
Empty set (0.00 sec)
#查询原表数据
mysql> select * from scholar1;
Empty set (0.00 sec)


mysql> create view emp_dept_view as select e.ename,e.sal,d.dname  from emp e join dept d on e.deptno =d.deptno;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from emp_dept_view;
+--------+---------+------------+
| ename  | sal     | dname      |
+--------+---------+------------+
| SMITH  |  800.00 | RESEARCH   |
| ALLEN  | 1600.00 | SALES      |
| WARD   | 1250.00 | SALES      |
| JONES  | 2975.00 | RESEARCH   |
| MARTIN | 1250.00 | SALES      |
| BLAKE  | 2850.00 | SALES      |
| CLARK  | 2450.00 | ACCOUNTING |
| SCOTT  | 3000.00 | RESEARCH   |
| KING   | 5000.00 | ACCOUNTING |
| TURNER | 1500.00 | SALES      |
| ADAMS  | 1100.00 | RESEARCH   |
| JAMES  |  950.00 | SALES      |
| FORD   | 3000.00 | RESEARCH   |
| MILLER | 1300.00 | ACCOUNTING |
+--------+---------+------------+
14 rows in set (0.00 sec)

mysql> update emp_dept_view set sal=1000 where dname ='ACCOUNTING';
Query OK, 3 rows affected (0.01 sec)
Rows matched: 3  Changed: 3  Warnings: 0

mysql> select * from emp_dept_view;
+--------+---------+------------+
| ename  | sal     | dname      |
+--------+---------+------------+
| SMITH  |  800.00 | RESEARCH   |
| ALLEN  | 1600.00 | SALES      |
| WARD   | 1250.00 | SALES      |
| JONES  | 2975.00 | RESEARCH   |
| MARTIN | 1250.00 | SALES      |
| BLAKE  | 2850.00 | SALES      |
| CLARK  | 1000.00 | ACCOUNTING |
| SCOTT  | 3000.00 | RESEARCH   |
| KING   | 1000.00 | ACCOUNTING |
| TURNER | 1500.00 | SALES      |
| ADAMS  | 1100.00 | RESEARCH   |
| JAMES  |  950.00 | SALES      |
| FORD   | 3000.00 | RESEARCH   |
| MILLER | 1000.00 | ACCOUNTING |
+--------+---------+------------+
14 rows in set (0.00 sec)

mysql> select * from emp;
+-------+--------+-----------+------+------------+---------+---------+--------+
| EMPNO | ENAME  | JOB       | MGR  | HIREDATE   | SAL     | COMM    | DEPTNO |
+-------+--------+-----------+------+------------+---------+---------+--------+
|  7369 | SMITH  | CLERK     | 7902 | 1980-12-17 |  800.00 |    NULL |     20 |
|  7499 | ALLEN  | SALESMAN  | 7698 | 1981-02-20 | 1600.00 |  300.00 |     30 |
|  7521 | WARD   | SALESMAN  | 7698 | 1981-02-22 | 1250.00 |  500.00 |     30 |
|  7566 | JONES  | MANAGER   | 7839 | 1981-04-02 | 2975.00 |    NULL |     20 |
|  7654 | MARTIN | SALESMAN  | 7698 | 1981-09-28 | 1250.00 | 1400.00 |     30 |
|  7698 | BLAKE  | MANAGER   | 7839 | 1981-05-01 | 2850.00 |    NULL |     30 |
|  7782 | CLARK  | MANAGER   | 7839 | 1981-06-09 | 1000.00 |    NULL |     10 |
|  7788 | SCOTT  | ANALYST   | 7566 | 1987-04-19 | 3000.00 |    NULL |     20 |
|  7839 | KING   | PRESIDENT | NULL | 1981-11-17 | 1000.00 |    NULL |     10 |
|  7844 | TURNER | SALESMAN  | 7698 | 1981-09-08 | 1500.00 |    0.00 |     30 |
|  7876 | ADAMS  | CLERK     | 7788 | 1987-05-23 | 1100.00 |    NULL |     20 |
|  7900 | JAMES  | CLERK     | 7698 | 1981-12-03 |  950.00 |    NULL |     30 |
|  7902 | FORD   | ANALYST   | 7566 | 1981-12-03 | 3000.00 |    NULL |     20 |
|  7934 | MILLER | CLERK     | 7782 | 1982-01-23 | 1000.00 |    NULL |     10 |
+-------+--------+-----------+------+------------+---------+---------+--------+
14 rows in set (0.00 sec)

说明：

①对于比较复杂且需要被多次反复使用的SQL语句，可以使用视图对象，简化开发，并且非常有利于后期的维护，在修改的时候，只需修改视图对象所映射的SQL语句即可。②使用视图和使用表是一样的，同样可以像对表一样对视图对象进行增删改查。
③视图对象存在在硬盘上，不会消失。
④视图对应的语句只能是DQL语句
基本操作：增删改查（CRUD）
增加（Create）、读取数据（Retrieve）、更新（Update）、删除（Delete）

DBA常用命令：

数据的导出？

在windows的dos窗口中

命令：mysqldump 数据库名<指定表> >导出的物理地址 -uroot -p密码

MYSQL学习之视图_视图_02

效果：

MYSQL学习之视图_视图_03

数据的导入？

命令： source 物理地址

说明：先登录到MYSQL服务器上，然后在使用该命令

步骤如下：

① 登录到MYSQL
② 创建一个新的数据库
③ 使用该数据库
④通过source来进行初始化数据

#创建一个空数据库
mysql> create database bjpowernode1;
Query OK, 1 row affected (0.01 sec)

#使用该数据库
mysql> use bjpowernode1;
Database changed

#导入数据进行初始化库
mysql> source F:\test\bjpowernode.sql
Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected, 1 warning (0.02 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 220 rows affected (0.00 sec)
Records: 220  Duplicates: 0  Warnings: 0

mysql> show tables;
+------------------------+
| Tables_in_bjpowernode1 |
+------------------------+
| bjpowernode            |
| dept                   |
| emp                    |
| emp_dept_view          |
| flower                 |
| salgrade               |
| scholar1               |
| scholar1_view          |
| scholor                |
| t_class                |
| t_student              |
| t_user                 |
| volunteer              |
| volunteer1             |
+------------------------+
14 rows in set (0.00 sec)

标签：rows,affected,0.00,视图,学习,sec,MYSQL,OK,Query
From： https://blog.51cto.com/u_15314328/5732598

（一）什么是视图？？

（二）基本操作

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