Modify mysql character set

MySQL is a popular relational database management system that is often used to develop Web applications. During the application development process, we often encounter situations where the MySQL character set needs to be modified, because the MySQL default character set may not necessarily meet our needs. This article will introduce how to modify the MySQL character set.

MySQL character set overview

MySQL supports multiple character sets and collation rules. A character set is a collection of available characters, and a collation is an algorithm for comparing and sorting characters. Common character sets include latin1, utf8, utf8mb4, etc.

In MySQL, each table and column can specify character sets and collation rules. If the character set is not explicitly specified, MySQL will set it according to the server's default character set. Therefore, before modifying the MySQL character set, we need to first understand the character set and collation rules currently used by the MySQL server and database.

View MySQL character set and collation rules

To view the MySQL server default character set and collation rules, you can use the following command:

mysql> show variables like 'character_set_server'; 
mysql> show variables like 'collation_server';

To view the character set used by the current database and collation rules, you can use the following command:

mysql> show variables like 'character_set_database'; 
mysql> show variables like 'collation_database';

To view the character set and collation rules of a table, you can use the following command:

mysql> show create table my_table;

This command will display the SQL statement that created the table. It will contain character set and collation rule information. To view the character set and collation rules of a column, you can use the following command:

mysql> show full columns from my_table;

This command will display the column information of the table, which contains character set and collation rule information.

Modify MySQL character set and collation rules

MySQL character set and collation rules can be set at multiple levels, including server level, database level, table level and column level. Below we will introduce how to set up at these levels respectively.

Modify server-level character set and collation rules

To modify the MySQL server default character set and collation rules, you can set them in the my.cnf file. This file is located in the /etc or /etc/mysql directory of the MySQL installation directory. In this file, you can set the following parameters:

[mysqld]
character-set-server=utf8mb4
collation-server=utf8mb4_unicode_ci

After the settings are completed, you need to restart the MySQL server to take effect.

Modify database-level character set and collation rules

To modify the character set and collation rules of the database, you can use the following command:

mysql> alter database my_database charset=utf8mb4 collate=utf8mb4_unicode_ci;

This command will modify the characters of the specified database Collection and proofreading rules. Note that modifying the character set and collation rules of a database will affect the character sets and collation rules of all tables in the database.

Modify table-level character set and collation rules

To modify the character set and collation rules of a table, you can use the following command:

mysql> alter table my_table charset=utf8mb4 collate=utf8mb4_unicode_ci;

This command will modify the characters of the specified table Collection and proofreading rules. Note that modifying the character set and collation rules of a table will affect the character set and collation rules of all columns in the table.

Modify column-level character set and collation rules

To modify the character set and collation rules of a column, you can use the following syntax:

mysql> alter table my_table modify column my_column varchar(50) charset=utf8mb4 collate=utf8mb4_unicode_ci;

This command will modify the characters of the specified column Collection and proofreading rules. Note that modifying the character set and collation rules of a column may affect the correctness of the application and requires caution.

Summary

MySQL character set and collation rules are one of the important parameters in MySQL development. When using MySQL to develop Web applications, it is usually necessary to modify MySQL's character set and collation rules according to the needs of the application. This article describes how to view the current MySQL server and database default character set and collation rules, and how to modify the character set and collation rules at the server level, database level, table level and column level respectively. I hope this article is helpful to you, thank you for reading!

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