【mysql】添加对emoji的支持

1、简介

涉及无线相关的 MySQL 数据库建议都提前采用 utf8mb4 字符集，避免 emoji 表情符号带来的问题

MySQL Server >  5.5.3

2、配置+升级

当前配置

mysql> s
--------------
mysql  Ver 14.14 Distrib 5.1.73, for redhat-linux-gnu (i386) using readline 5.1

Connection id:          3
Current database:
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.6.25-debug-log Source distribution
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    utf8mb4
Db     characterset:    utf8mb4
Client characterset:    utf8mb4
Conn.  characterset:    utf8mb4
UNIX socket:            /data/mysql/mysql.sock
Uptime:                 46 min 53 sec

更改数据库/表

ALTER DATABASE dbname CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;
ALTER TABLE tbname CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
ALTER TABLE tbname CHANGE old_column_name new_column_name VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

my.cnf配置

[client]  
default-character-set = utf8mb4  
 
[mysql]  
default-character-set = utf8mb4  
 
[mysqld]  
character-set-client-handshake = FALSE  
character-set-server = utf8mb4  
collation-server = utf8mb4_general_ci  
init_connect='SET NAMES utf8mb4'

 /usr/share/mysql/charsets/Index.xml配置

<charset name="utf8mb4">
  <family>Unicode</family>
  <description>UTF-8 Unicode</description>
  <alias>utf-8</alias>
  <collation name="utf8_general_ci"     id="33">
   <flag>primary</flag>
   <flag>compiled</flag>
  </collation>
  <collation name="utf8_bin"            id="83">
    <flag>binary</flag>
    <flag>compiled</flag>
  </collation>
</charset>

查看字符集

mysql> show variables where variable_name like 'character_set%' or variable_name like 'coll%';
+--------------------------+----------------------------------+
| Variable_name            | Value                            |
+--------------------------+----------------------------------+
| character_set_client     | utf8                             |
| character_set_connection | utf8                             |
| character_set_database   | utf8                             |
| character_set_filesystem | binary                           |
| character_set_results    | utf8                             |
| character_set_server     | utf8                             |
| character_set_system     | utf8                             |
| character_sets_dir       | /u01/mysql/share/mysql/charsets/ |
| collation_connection     | utf8_general_ci                  |
| collation_database       | utf8_general_ci                  |
| collation_server         | utf8_general_ci                  |
+--------------------------+----------------------------------+
11 rows in set (0.00 sec)
	
mysql> show char set;
+----------+-----------------------------+---------------------+--------+
| Charset  | Description                 | Default collation   | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5     | Big5 Traditional Chinese    | big5_chinese_ci     |      2 |
| dec8     | DEC West European           | dec8_swedish_ci     |      1 |
| cp850    | DOS West European           | cp850_general_ci    |      1 |
| hp8      | HP West European            | hp8_english_ci      |      1 |
| koi8r    | KOI8-R Relcom Russian       | koi8r_general_ci    |      1 |
| latin1   | cp1252 West European        | latin1_swedish_ci   |      1 |
| latin2   | ISO 8859-2 Central European | latin2_general_ci   |      1 |
| swe7     | 7bit Swedish                | swe7_swedish_ci     |      1 |
| ascii    | US ASCII                    | ascii_general_ci    |      1 |
| ujis     | EUC-JP Japanese             | ujis_japanese_ci    |      3 |
| sjis     | Shift-JIS Japanese          | sjis_japanese_ci    |      2 |
| hebrew   | ISO 8859-8 Hebrew           | hebrew_general_ci   |      1 |
| tis620   | TIS620 Thai                 | tis620_thai_ci      |      1 |
| euckr    | EUC-KR Korean               | euckr_korean_ci     |      2 |
| koi8u    | KOI8-U Ukrainian            | koi8u_general_ci    |      1 |
| gb2312   | GB2312 Simplified Chinese   | gb2312_chinese_ci   |      2 |
| greek    | ISO 8859-7 Greek            | greek_general_ci    |      1 |
| eucjpms  | UJIS for Windows Japanese   | eucjpms_japanese_ci |      3 |
+----------+-----------------------------+---------------------+--------+
40 rows in set (0.00 sec)

mysql> show COLLATION;
+--------------------------+----------+-----+---------+----------+---------+
| Collation                | Charset  | Id  | Default | Compiled | Sortlen |
+--------------------------+----------+-----+---------+----------+---------+
| big5_chinese_ci          | big5     |   1 | Yes     | Yes      |       1 |
| big5_bin                 | big5     |  84 |         | Yes      |       1 |
| dec8_swedish_ci          | dec8     |   3 | Yes     | Yes      |       1 |
| dec8_bin                 | dec8     |  69 |         | Yes      |       1 |
| cp850_general_ci         | cp850    |   4 | Yes     | Yes      |       1 |
| eucjpms_bin              | eucjpms  |  98 |         | Yes      |       1 |
+--------------------------+----------+-----+---------+----------+---------+
219 rows in set (0.01 sec)

– character_set_server：默认的内部操作字符集

– character_set_client：客户端来源数据使用的字符集

– character_set_connection：连接层字符集

– character_set_results：查询结果字符集

– character_set_database：当前选中数据库的默认字符集

– character_set_system：系统元数据(字段名等)字符集

MySQL中的字符序名称遵从命名惯例

以字符序对应的字符集名称开头；以_ci(表示大小写不敏感 case ignore )、_cs(表示大小写敏感 case sensitive )或_bin(表示按编码值比较)结尾。

例如：在字符序“utf8_general_ci”下，字符“a”和“A”是等价的

MySQL中的字符集转换过程

1. MySQL Server收到请求时将请求数据从character_set_client转换为character_set_connection；

2. 进行内部操作前将请求数据从character_set_connection转换为内部操作字符集，其确定方法如下：

• 使用每个数据字段的CHARACTER SET设定值；

• 若上述值不存在，则使用对应数据表的DEFAULT CHARACTER SET设定值(MySQL扩展，非SQL标准)；

• 若上述值不存在，则使用对应数据库的DEFAULT CHARACTER SET设定值；

• 若上述值不存在，则使用character_set_server设定值。

3. 将操作结果从内部操作字符集转换为character_set_results。

三、emoji表情与utf8mb4

emoji表情mysql的utf8是不支持，需要修改设置为utf8mb4

在MYSQL 5.5 之前， UTF8 编码只支持1-3个字节，只支持BMP这部分的unicode编码区， 关于BMP，http://en.wikipedia.org/wiki/Mapping_of_Unicode_characters 这里看，基本就是0000～FFFF这一区。

从MYSQL5.5开始，可支持4个字节UTF编码utf8mb4，一个字符最多能有4字节，所以能支持更多的字符集，utf8mb4兼容utf8，且比utf8能表示更多的字符

CREATE TABLE `ios_emoji` (  
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '自增ID',  
  `unicode` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT 'Unicode编码',  
  `utf8` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT 'UTF8编码',  
  `utf16` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT 'UTF16编码',  
  `sbunicode` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT 'SBUnicode编码',  
  `filename` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '文件名',  
  `filebyte` longblob COMMENT '文件内容字节',  
  PRIMARY KEY (`id`)  
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=COMPACT COMMENT='ios表情编码表'; 

　　

参考文章

http://drupal.stackexchange.com/questions/166405/why-are-we-using-utf8mb4-general-ci-and-not-utf8mb4-unicode-ci

http://stackoverflow.com/questions/766809/whats-the-difference-between-utf8-general-ci-and-utf8-unicode-ci

http://blog.csdn.net/leshami/article/details/42024217

http://www.laruence.com/2008/01/05/12.html