让 MySQL 支持 emoji 存储

要让 MySQL 开启 utf8mb4 支持，需要一些额外的设置。

1. 检查 MySQL Server 版本

• utf8mb4 支持需要 MySQL Server v5.5.3+

2. 设置表的 CHARSET

• 创建表的时候指定 CHARSET 为 utf8mb4

  CREATE TABLE IF NOT EXISTS table_name (
  ...
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE utf8mb4_general_ci;

• 或者修改已存在的表 CHARSET 为 utf8mb4

  ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

3. 修改 MySQL 配置文件

• 修改 my.conf 的内容

  [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

4. 检查是否生效

• 正常情况下的结果应该如下所示：

  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 |
  +--------------------------+--------------------+

5. 指定 MySQL 连接时的 charset

• 以 mysql-python 为例：

  MySQLdb.connect(
          host=config.DB_HOST,
          port=config.DB_PORT,
          user=config.DB_USR,
          passwd=config.DB_PSW,
          db=config.DB_NAME,
          use_unicode=True,
          charset="utf8mb4")

[1] http://en.wikipedia.org/wiki/Mapping_of_Unicode_characters

[2] https://mathiasbynens.be/notes/mysql-utf8mb4#utf8-to-utf8mb4