mysql 字符集

查看mysql支持的字符集：

mysql> SHOW CHARACTER SET;
+----------+---------------------------------+---------------------+--------+
| Charset  | Description                     | Default collation   | Maxlen |
+----------+---------------------------------+---------------------+--------+
| big5     | Big5 Traditional Chinese        | big5_chinese_ci     |      2 |
...
| latin1   | cp1252 West European            | latin1_swedish_ci   |      1 |
| latin2   | ISO 8859-2 Central European     | latin2_general_ci   |      1 |
...
| utf8     | UTF-8 Unicode                   | utf8_general_ci     |      3 |
| ucs2     | UCS-2 Unicode                   | ucs2_general_ci     |      2 |
...
| utf8mb4  | UTF-8 Unicode                   | utf8mb4_general_ci  |      4 |
...
| binary   | Binary pseudo charset           | binary              |      1 |
...

,查看字符集支持的排序规则：

mysql> SHOW COLLATION WHERE Charset = 'latin1';
+-------------------+---------+----+---------+----------+---------+
| Collation         | Charset | Id | Default | Compiled | Sortlen |
+-------------------+---------+----+---------+----------+---------+
| latin1_german1_ci | latin1  |  5 |         | Yes      |       1 |
| latin1_swedish_ci | latin1  |  8 | Yes     | Yes      |       1 |
| latin1_danish_ci  | latin1  | 15 |         | Yes      |       1 |
| latin1_german2_ci | latin1  | 31 |         | Yes      |       2 |
| latin1_bin        | latin1  | 47 |         | Yes      |       1 |
| latin1_general_ci | latin1  | 48 |         | Yes      |       1 |
| latin1_general_cs | latin1  | 49 |         | Yes      |       1 |
| latin1_spanish_ci | latin1  | 94 |         | Yes      |       1 |
+-------------------+---------+----+---------+----------+---------+

ASCII:包含Unicode 码中U+0000 to U+007F 范围的字符
UNICODE:包含Unicode码中U+0000 to U+10FFFF范围的字符
可以看出，ASCII 是UNICODE 的子集。

排序规则大小写敏感后缀

后缀	备注
_ai	重音不敏感
_as	重音敏感
_ci	大小写不敏感
_cs	大小写敏感
_bin	二进制

_ci 暗含_ai，_cs 暗含_as。
对于二进制字符集的二进制排序规则，是基于字节值比较；对于非二进制字符集的_bin 排序规则，比较是基于字符的数字之，这和多字节字符的字节值不一样。