字符集是字符的编码规则，校对规则是对字符集中的字符比较大小。由于字符集和校对规则之间相互关联，因此如果只修改字符集，校对规则也会跟着变化，而如果只修改校对规则，字符集则也会跟着变化。

StoneDB支持的字符集

> show character 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 |
+----------+---------------------------------+---------------------+--------+

字符集的变量

> show variables like '%char%';
+--------------------------+----------------------------------+
| Variable_name            | Value                            |
+--------------------------+----------------------------------+
| character_set_client     | utf8                             |
| character_set_connection | utf8                             |
| character_set_database   | utf8mb4                          |
| character_set_filesystem | binary                           |
| character_set_results    | utf8                             |
| character_set_server     | utf8mb4                          |
| character_set_system     | utf8                             |
| character_sets_dir       | /stonedb/install/share/charsets/ |
+--------------------------+----------------------------------+
8 rows in set (0.01 sec)

1）客户端向服务端发送请求使用的字符集：取决于操作系统的字符集，LC_ALL、LC_CTYPE、LANG决定了操作系统使用的字符集，优先级依次从高到底
2）服务端接收客户端请求使用的字符集：取决于变量character_set_client
3）服务端在运行过程中转换使用的字符集：取决于变量character_set_connection
4）服务端向客户端返回请求使用的字符集：取决于变量character_set_results
5）客户端接收服务端响应使用的字符集：取决于操作系统的字符集
假设服务端使用的字符集为utf8，客户端启动时使用了–default-character-set=gbk选项，那么character_set_client、character_set_connection、character_set_results都会被设置为gbk。假如某张表中存储了中文，那么服务端和客户端这些中文的字符编码是不同的，在Unix操作系统中服务端会根据character_set_connection进行转换，很显然客户端收到的结果是乱码。
StoneDB默认的字符集取决于变量character_set_server，如果创建的数据库没有指定字符集，默认的字符集就是变量character_set_server的值。如果创建的表没有指定字符集，继承的是数据库的字符集。StoneDB的表一旦被创建后，字符集就不能被修改和转换。