MySQL utf8mb4 字符集：支持 emoji 表情符号

      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)