Introduce the concept and operation of views in mysql
Concept
<a href="http://www.php.cn/code/8708.html" target="_blank">View</a>
is a virtual table, for users who use view , basically the same as using a normal table. The view does not exist in the database, and the data in the view is dynamically generated.
Advantages of views over ordinary tables:
Simplicity: When using views, you do not need to care about the corresponding structural conditions of subsequent tables. For users, views are filtered results. set.
Security: Users can only access the result sets for which they are allowed queries.
Data independence: Once the view structure is determined, changes to the actual table have no impact on view users.
View operations
View operations are divided into Create view
, Modify view
, <a href="http://www.php.cn/php/php-tp-remove.html" target="_blank">Delete </a>View
, View view definition
.
Create view, modify view
#创建视图 create [or replace] [algorithm={undefined|merge|temptable}] view view_name[(column_list)] as select_statement [with[cascaded|local] check option] # 修改视图 alter [algorithm={undefined|merge|temptable}] view view_name[(column_list)] as select_statement [with[cascaded|local] check option]
Example:
create view view_test as select t1.sid,t1.username,t2.department from test1 t1 left join test2 t2 on t1.sid=t2.sid;
Create view
Note:
The from keyword cannot contain a subquery;
The view that cannot be updated: contains aggregate function/group/distinct /having/union, constant view, select contains subquery, jion, from a view that cannot be updated, where subquery refers to the table in the from clause.
with[cascaded|local] check option Absolutely allows updating data so that the record no longer meets the view conditions. Among them,
local-only the conditions of this view can be updated
,cascaded-the conditions of all views for this view must be met before
can be updated. The default is cascaded.
View view data
Same as ordinary table
select * from view_test;
View View data
Delete view
#删除视图 drop view [if exists] view_name [,view_name2]...[restrict|cascade] #举例 drop view view_test;
View view status
Starting from MySQL5.1, when using the show tables command Not only the table names but also the view names are displayed.
【Related recommendations】
1. Free mysql online video tutorial
2. MySQL latest manual tutorial
3. Those things about database design
The above is the detailed content of Introduce the concept and operation of views in mysql. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

The main role of MySQL in web applications is to store and manage data. 1.MySQL efficiently processes user information, product catalogs, transaction records and other data. 2. Through SQL query, developers can extract information from the database to generate dynamic content. 3.MySQL works based on the client-server model to ensure acceptable query speed.

The process of starting MySQL in Docker consists of the following steps: Pull the MySQL image to create and start the container, set the root user password, and map the port verification connection Create the database and the user grants all permissions to the database

Laravel is a PHP framework for easy building of web applications. It provides a range of powerful features including: Installation: Install the Laravel CLI globally with Composer and create applications in the project directory. Routing: Define the relationship between the URL and the handler in routes/web.php. View: Create a view in resources/views to render the application's interface. Database Integration: Provides out-of-the-box integration with databases such as MySQL and uses migration to create and modify tables. Model and Controller: The model represents the database entity and the controller processes HTTP requests.

I encountered a tricky problem when developing a small application: the need to quickly integrate a lightweight database operation library. After trying multiple libraries, I found that they either have too much functionality or are not very compatible. Eventually, I found minii/db, a simplified version based on Yii2 that solved my problem perfectly.

The key to installing MySQL elegantly is to add the official MySQL repository. The specific steps are as follows: Download the MySQL official GPG key to prevent phishing attacks. Add MySQL repository file: rpm -Uvh https://dev.mysql.com/get/mysql80-community-release-el7-3.noarch.rpm Update yum repository cache: yum update installation MySQL: yum install mysql-server startup MySQL service: systemctl start mysqld set up booting

Installing MySQL on CentOS involves the following steps: Adding the appropriate MySQL yum source. Execute the yum install mysql-server command to install the MySQL server. Use the mysql_secure_installation command to make security settings, such as setting the root user password. Customize the MySQL configuration file as needed. Tune MySQL parameters and optimize databases for performance.

Article summary: This article provides detailed step-by-step instructions to guide readers on how to easily install the Laravel framework. Laravel is a powerful PHP framework that speeds up the development process of web applications. This tutorial covers the installation process from system requirements to configuring databases and setting up routing. By following these steps, readers can quickly and efficiently lay a solid foundation for their Laravel project.

Compared with other programming languages, MySQL is mainly used to store and manage data, while other languages such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages have advantages in their respective fields such as data analytics, enterprise applications, and system programming.
