MySQL utf8mb4 字符集：支持 emoji 表情符号-优快云博客

本文详细介绍了如何将移动互联网行业的MySQL数据库升级至utf8mb4字符集，包括必要条件、升级步骤及关键配置，确保解决emoji表情符号问题，提升数据库性能。

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㈠序言

为了应对无线互联网的机遇和挑战、避免 emoji 表情符号带来的问题、
涉及无线相关的 MySQL 数据库建议都提前采用 utf8mb4 字符集
这必须要作为移动互联网行业的一个技术选型的要点

㈡限制

需要 >= MySQL 5.5.3版本、从库也必须是5.5的了、低版本不支持这个字符集、复制报错

㈢简要步骤

以下是一个未升级到 5.5.3 的配置步骤：

① 备份数据库
② 升级 MySQL Server 到 v5.5.3+

③ 修改 database、table和column字符集

# For each database:ALTER DATABASE database_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;# For each table:ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;# For each column:ALTER TABLE table_name CHANGE column_name column_name VARCHAR(191) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;# (Don’t blindly copy-paste this! The exact statement depends on the column type, maximum length, and other properties. The above line is just an example for a `VARCHAR` column.)
④ 修改 my.cnf

[client]
default-character-set = utf8mb4

[mysql]
default-character-set = utf8mb4

[mysqld]
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
init_connect='SET NAMES utf8mb4'

⑤ 重启 MySQL Server、检查字符集

mysql> SHOW VARIABLES WHERE Variable_name LIKE 'character\_set\_%' OR Variable_name LIKE 'collation%';
+--------------------------+--------------------+
| Variable_name            | Value              |
+--------------------------+--------------------+
| character_set_client     | utf8mb4            |
| character_set_connection | utf8mb4            |
| character_set_database   | utf8mb4            |
| character_set_filesystem | binary             |
| character_set_results    | utf8mb4            |
| character_set_server     | utf8mb4            |
| character_set_system     | utf8               |
| collation_connection     | utf8mb4_unicode_ci |
| collation_database       | utf8mb4_unicode_ci |
| collation_server         | utf8mb4_unicode_ci |
+--------------------------+--------------------+
 rows in set (0.00 sec)