An explanation of the two-column data method in mysql exchange table
1. Create tables and records for testing
CREATE TABLE `product` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '产品id', `name` varchar(50) NOT NULL COMMENT '产品名称', `original_price` decimal(5,2) unsigned NOT NULL COMMENT '原价', `price` decimal(5,2) unsigned NOT NULL COMMENT '现价', PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;INSERT INTO `product` (`id`, `name`, `original_price`, `price`) VALUES (NULL, '雪糕', '5', '3.5'), (NULL, '鲜花', '18', '15'), (NULL, '甜点', '25', '12.5'), (NULL, '玩具', '55', '45'), (NULL, '钱包', '285', '195');
mysql> select * from product; +----+--------+----------------+--------+| id | name | original_price | price | +----+--------+----------------+--------+| 1 | 雪糕 | 5.00 | 3.50 | | 2 | 鲜花 | 18.00 | 15.00 | | 3 | 甜点 | 25.00 | 12.50 | | 4 | 玩具 | 55.00 | 45.00 || 5 | 钱包 | 285.00 | 195.00 | +----+--------+----------------+--------+5 rows in set (0.00 sec)
2. Exchange the values of original_price and price
Novices may use the following methods to exchange
update product set original_price=price,price=original_price;
But the result of this execution will only make the values of original_price and price both be the value of price, because update is sequential,
execute firstoriginal_price=price , the value of original_price has been updated to price,
Then execute price=original_price, which is equivalent to no update.
Execution result:
mysql> select * from product; +----+--------+----------------+--------+| id | name | original_price | price | +----+--------+----------------+--------+| 1 | 雪糕 | 5.00 | 3.50 | | 2 | 鲜花 | 18.00 | 15.00 | | 3 | 甜点 | 25.00 | 12.50 | | 4 | 玩具 | 55.00 | 45.00 || 5 | 钱包 | 285.00 | 195.00 | +----+--------+----------------+--------+5 rows in set (0.00 sec) mysql> update product set original_price=price,price=original_price; Query OK, 5 rows affected (0.00 sec) Rows matched: 5 Changed: 5 Warnings: 0mysql> select * from product; +----+--------+----------------+--------+| id | name | original_price | price | +----+--------+----------------+--------+| 1 | 雪糕 | 3.50 | 3.50 | | 2 | 鲜花 | 15.00 | 15.00 | | 3 | 甜点 | 12.50 | 12.50 | | 4 | 玩具 | 45.00 | 45.00 || 5 | 钱包 | 195.00 | 195.00 | +----+--------+----------------+--------+5 rows in set (0.00 sec)
The correct exchange method is as follows:
update product as a, product as b set a.original_price=b.price, a.price=b.original_price where a.id=b.id;
Execution results:
mysql> select * from product; +----+--------+----------------+--------+| id | name | original_price | price | +----+--------+----------------+--------+| 1 | 雪糕 | 5.00 | 3.50 | | 2 | 鲜花 | 18.00 | 15.00 | | 3 | 甜点 | 25.00 | 12.50 | | 4 | 玩具 | 55.00 | 45.00 || 5 | 钱包 | 285.00 | 195.00 | +----+--------+----------------+--------+5 rows in set (0.00 sec) mysql> update product as a, product as b set a.original_price=b.price, a.price=b.original_price where a.id=b.id; Query OK, 5 rows affected (0.01 sec) Rows matched: 5 Changed: 5 Warnings: 0mysql> select * from product; +----+--------+----------------+--------+| id | name | original_price | price | +----+--------+----------------+--------+| 1 | 雪糕 | 3.50 | 5.00 | | 2 | 鲜花 | 15.00 | 18.00 | | 3 | 甜点 | 12.50 | 25.00 | | 4 | 玩具 | 45.00 | 55.00 || 5 | 钱包 | 195.00 | 285.00 | +----+--------+----------------+--------+5 rows in set (0.00 sec)
This article explains the two-column data method in the mysql exchange table. For more information, please pay attention to php' Chinese website.
Related recommendations:
How to generate 0~1 random decimal method through php
About the use of mysql timestamp formatting function from_unixtime Instructions
Instructions on the use of mysql functions concat and group_concat
The above is the detailed content of An explanation of the two-column data method in mysql exchange table. 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
MySQL: An Introduction to the World's Most Popular Database
Apr 12, 2025 am 12:18 AM
MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.
How to open phpmyadmin
Apr 10, 2025 pm 10:51 PM
You can open phpMyAdmin through the following steps: 1. Log in to the website control panel; 2. Find and click the phpMyAdmin icon; 3. Enter MySQL credentials; 4. Click "Login".
Why Use MySQL? Benefits and Advantages
Apr 12, 2025 am 12:17 AM
MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.
MySQL's Place: Databases and Programming
Apr 13, 2025 am 12:18 AM
MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen
How to connect to the database of apache
Apr 13, 2025 pm 01:03 PM
Apache connects to a database requires the following steps: Install the database driver. Configure the web.xml file to create a connection pool. Create a JDBC data source and specify the connection settings. Use the JDBC API to access the database from Java code, including getting connections, creating statements, binding parameters, executing queries or updates, and processing results.
How to start mysql by docker
Apr 15, 2025 pm 12:09 PM
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
MySQL's Role: Databases in Web Applications
Apr 17, 2025 am 12:23 AM
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.
How to install mysql in centos7
Apr 14, 2025 pm 08:30 PM
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
