utf8mb4 utf8mb3 utf8
Refer to
MySQL在5.5.3之后增加了utf8mb4字符编码，mb4即most bytes 4。简单说utf8mb4是utf8的超集并完全兼容utf8，能够用四个字节存储更多的字符。而utf8是utf8mb3的别名。标准的UTF-8字符集编码是可以用1~4个字节去编码21位字符，但是MySQL其实实现的utf8只是使用3个字节而已，utf8mb4才是真正意义上的utf8。
如果数据库表字段设置的字符集不是utf8mb4，却插入类似emjoy表情的时候：
- 严格模式下会出现Incorrect string value: /xF0/xA1/x8B/xBE/xE5/xA2… for column 'name'这样的错误
- 非严格模式下此后的数据会被截断
排序字符集
Refer to: Collation Naming Conventions
| Suffix | Meaning | Remark |
|---|---|---|
| _ai | Accent insensitive | |
| _as | Accent sensitive | |
| _ci | Case insensitive | 不分区大小写 |
| _cs | case-sensitive | 区分大小写 |
| _bin | Binary | 二进制存储，区分大小写 |
utf8mb4_ unicode_ ci VS utf8mb4_ general_ ci
Refer to: What's the difference between utf8_general_ci and utf8_unicode_ci
- utf8_general_ci校对速度快，但准确度稍差。
- utf8_unicode_ci准确度高，但校对速度稍慢。
数据库一般默认选择utf8mb4_general_ci;
如果应用有德语、法语或者俄语，请一定使用utf8mb4_unicode_ci
配置
vim /etc/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_general_ci
init_connect='SET NAMES utf8mb4'
检查目前MySQL的字符集
mysql> SHOW VARIABLES WHERE Variable_name LIKE 'character\_set\_%' OR Variable_name LIKE 'collation%';
+--------------------------+-----------------+
| 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 |
| collation_connection | utf8_general_ci |
| collation_database | utf8_general_ci |
| collation_server | utf8_general_ci |
+--------------------------+-----------------+
10 rows in set (0.00 sec)
总结
- MySQL版本5.5.3+
- MySQL Connector/J Java驱动5.1.13+
- /etc/my.cnf配置中添加配置，详见上面
- 排序字符集选用utf8mb4_unicode_ci
- 列（字段）> 表 > 数据库
备注：
其实只要数据库支持utfbmb4(show char set)，及时MySQL配置(/etc/my.cnf)中配置的默认字符集是utf8，也可以直接指定数据库、表、字段的字符集为utf8mb4，然后在连接的时候指定字符集为utf8mb4即可。
比如设置Java的连接参数中characterEncoding=utf8mb4
查看MySQL支持的字符集列表：
root@localhost:3306.sock [test]> 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 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp866 | DOS Russian | cp866_general_ci | 1 |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci | 1 |
| macce | Mac Central European | macce_general_ci | 1 |
| macroman | Mac West European | macroman_general_ci | 1 |
| cp852 | DOS Central European | cp852_general_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| utf16 | UTF-16 Unicode | utf16_general_ci | 4 |
| utf16le | UTF-16LE Unicode | utf16le_general_ci | 4 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| utf32 | UTF-32 Unicode | utf32_general_ci | 4 |
| binary | Binary pseudo charset | binary | 1 |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci | 1 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
| gb18030 | China National Standard GB18030 | gb18030_chinese_ci | 4 |
+----------+---------------------------------+---------------------+--------+
41 rows in set (0.00 sec)
建议
数据库在设置字符集的时候，设置成utf8mb4格式！