MySQL常用数据表操作SQL
作为程序开发员, 经常要导入导出一些数据, 今天就把我导入导出数据的一些SQL分享一下: 下文中所有的测试语句数据表明都用 tablename 1. 导出表结构 show create table tablename; 2. 导出一个表的数据到外部文件 select * into outfile '/tmp/data.txt' f
作为程序开发员, 经常要导入导出一些数据, 今天就把我导入导出数据的一些SQL分享一下:
下文中所有的测试语句数据表明都用 tablename
1. 导出表结构
show create table tablename;
2. 导出一个表的数据到外部文件
select * into outfile '/tmp/data.txt' from tablename;
输出的文件格式默认每条记录以 \n (换行符)分割, 每个字段之间以 \t (TAB键)分割, 可以自定义分隔符, 请查手册
3. 把表里边的数据导入到另外的数据表
当两个数据表的字段一样且顺序相同, 可以不用列举每一个字段:
insert into tablename1 select * from tablename2
如果字段不同, 或者
insert into tablename1 (column1, column2) select column3 as column1, column4 as column2 from tablename2;
不管是连表查询, group limit 等操作生成的结果也可以存储到另外的数据表中, 不过你要使用别名保证数据表字段相对应
insert into tablename1(column1, column2) select a.column3 as column1 , b.column4 as column2 from tablename2 a, tablename3 b on a.column4=b.column4 limit100
4. 从文件中导入数据到数据表
load data infile '/tmp/data.txt' into table tablename.
默认的外部文件, 记录分隔符是 \n (换行符), 字段的分隔符是 \t (Tab键) , 当然也可以自己指定分隔符, 具体的参数查手册!
5. 直接创建表并把查询结果保存到新的表
create table tablename1 select * from table2
后边的SQL语句也支持 group, limit, join, union 等操作, 不在演示, 自己动手尝试
OK , 数据表操作常用SQL就这些了, 请继续关注我的博客: http://www.phpv5.com , 有问题我们共同探讨h
声明: 本文采用 CC BY-NC-SA 3.0 协议进行授权
转载请注明来源:小景的博客
本文链接地址:http://www.phpv5.com/blog/archives/232/

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.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.
