mysql的字符集设置众多,从客户端到连接到结果集,从服务器到库到表到列,都可以设置字符集,灵活很强大,但就是很容易出问题,如
mysql的字符集设置众多,从客户端到连接到结果集,从服务器到库到表到列,都可以设置字符集,灵活很强大,但就是很容易出问题,如果不了解其机制,很容易就出现乱码问题。
为了普度众生,让大家尽量在工作中少受或者不受乱码的骚扰、困扰,这里我结合之前其它同学在论坛的发帖,并结合自己的理解和实践,详细分析总结了一下,以飨各位看官。
关于字符集和乱码的基础知识这里就不详细说明了(请自行搜索),但有一个问题需要特别强调一下:乱码是怎么产生的?
这个问题相信很多同学都是模棱两可,或者没有认真想过,反正理解就是”字符编码“不对导致乱码,但没有真正想过为什么”字符编码“会导致乱码。
答案其实很简单:“转换导致乱码”!
根据这个原则来判断,各种情况就很简单了:
1)数据传送过程中不会导致乱码
2)数据存储不会导致乱码
3)数据输入和输出(包括显示)可能导致乱码
4)数据接收和发送可能导致乱码
更详细的解释:转换导致乱码是指本来是A字符集的数据被当成了B字符集进行解析,而不是说正确的A字符集转换为B字符集。
例如:如下mysql字符处理机制流程图中,mysql客户端发送的实际上是2个gbk字符(4字节),但character_set_connection
设置了utf8,于是mysql服务器将收到的4字节gbk数据按照utf8解析,得到1个中文字符+1个字节,这时就产生乱码了;
如果character_set_connection 设置为gbk,mysql服务器收到数据后按照gbk解析,得到两个正确的中文,然后再转换为这两个中文对应的utf8编码,,这就不会产生乱码。)
【mysql的字符处理机制】
详细的处理机制如下图:
我们模拟一下一条数据从插入到读取的处理流程,看看在整个流程中,字符集是如何辗转腾挪的。
【插入流程】
1. 客户端设定了自己的编码(character_set_client),接收用户的输入;
2. 客户端将用户的输入“转换”成连接的编码(character_set_connection) =====> 第一次转换
3. 客户端将转换后的数据发送给服务器; =====> 传输不会导致编码转换
4. 服务器收到客户端的数据,再判断数据列的字符集,进行字符转换 =====> 第二次转换
5. 服务器将数据存储(例如磁盘) =====> 存储不会导致编码转换

InnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.

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.

MySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.

MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

MySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.

SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA


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

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

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

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

Dreamweaver Mac version
Visual web development tools

WebStorm Mac version
Useful JavaScript development tools

Zend Studio 13.0.1
Powerful PHP integrated development environment