MySQL数据库utf8表存储latin1乱码字符转换
线上有个数据表,字符集是utf8,但由于环境不统一的原因,导致实际上数据表存储的内容是latin1内码的数据。 也就是说,借着utf8的壳子,实际存储着latin1字符集的数据。 在这种情况下,需要注意几个字符集配置: 客户端终端工具(SecureCRT)的显示字符集设置
线上有个数据表,字符集是utf8,但由于环境不统一的原因,导致实际上数据表存储的内容是latin1内码的数据。也就是说,借着utf8的壳子,实际存储着latin1字符集的数据。在这种情况下,需要注意几个字符集配置:
客户端终端工具(SecureCRT)的显示字符集设置为:utf-8;
Linux终端(TERM)下,设置LANG环境变量为:en_US.UTF-8,或者zh_CN.UTF-8;
连接到MySQL后,设置client/connect字符集为:latin1 (set names latin1)。
完成上述设置后,在Linux命令行的mysql cli客户端中才能正常显示中文。
为了统一,需要将这些数据的内码也转成utf8才行,可以按以下几个步骤完成:
用latin1字符集将原始数据导出,确保在本地客户端(中文环境)下用文本编辑器可以正常查看;
用文本编辑器另存为utf-8字符集后上传到server端 或者 把数据直接拷贝到;
Linux终端下,新建一个文件,直接将数据粘贴进去;
清空数据表(truncate),修改字符集(alter table xx default charset = utf8);
将文本导入到数据表中。
上面是比较笨的手工操作方法,以演示整个过程。
如果表里存储比较复杂的数据时,建议写程序进行转换,毕竟内码不同,无法直接在线转换。
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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.

MySQL is an open source relational database management system suitable for data storage, management, query and security. 1. It supports a variety of operating systems and is widely used in Web applications and other fields. 2. Through the client-server architecture and different storage engines, MySQL processes data efficiently. 3. Basic usage includes creating databases and tables, inserting, querying and updating data. 4. Advanced usage involves complex queries and stored procedures. 5. Common errors can be debugged through the EXPLAIN statement. 6. Performance optimization includes the rational use of indexes and optimized query statements.

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.

InnoDB's lock mechanisms include shared locks, exclusive locks, intention locks, record locks, gap locks and next key locks. 1. Shared lock allows transactions to read data without preventing other transactions from reading. 2. Exclusive lock prevents other transactions from reading and modifying data. 3. Intention lock optimizes lock efficiency. 4. Record lock lock index record. 5. Gap lock locks index recording gap. 6. The next key lock is a combination of record lock and gap lock to ensure data consistency.

The main reasons for poor MySQL query performance include not using indexes, wrong execution plan selection by the query optimizer, unreasonable table design, excessive data volume and lock competition. 1. No index causes slow querying, and adding indexes can significantly improve performance. 2. Use the EXPLAIN command to analyze the query plan and find out the optimizer error. 3. Reconstructing the table structure and optimizing JOIN conditions can improve table design problems. 4. When the data volume is large, partitioning and table division strategies are adopted. 5. In a high concurrency environment, optimizing transactions and locking strategies can reduce lock competition.

In database optimization, indexing strategies should be selected according to query requirements: 1. When the query involves multiple columns and the order of conditions is fixed, use composite indexes; 2. When the query involves multiple columns but the order of conditions is not fixed, use multiple single-column indexes. Composite indexes are suitable for optimizing multi-column queries, while single-column indexes are suitable for single-column queries.

To optimize MySQL slow query, slowquerylog and performance_schema need to be used: 1. Enable slowquerylog and set thresholds to record slow query; 2. Use performance_schema to analyze query execution details, find out performance bottlenecks and optimize.

MySQL and SQL are essential skills for developers. 1.MySQL is an open source relational database management system, and SQL is the standard language used to manage and operate databases. 2.MySQL supports multiple storage engines through efficient data storage and retrieval functions, and SQL completes complex data operations through simple statements. 3. Examples of usage include basic queries and advanced queries, such as filtering and sorting by condition. 4. Common errors include syntax errors and performance issues, which can be optimized by checking SQL statements and using EXPLAIN commands. 5. Performance optimization techniques include using indexes, avoiding full table scanning, optimizing JOIN operations and improving code readability.


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