同样的，通过查询information_schema.collations也可以：
mysql> select * from information_schema.collations where character_set_name = "utf8mb4"; +------------------------+--------------------+-----+------------+-------------+---------+ | COLLATION_NAME | CHARACTER_SET_NAME | ID | IS_DEFAULT | IS_COMPILED | SORTLEN | +------------------------+--------------------+-----+------------+-------------+---------+ | utf8mb4_general_ci | utf8mb4 | 45 | Yes | Yes | 1 | | utf8mb4_bin | utf8mb4 | 46 | | Yes | 1 | | utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 8 | | utf8mb4_icelandic_ci | utf8mb4 | 225 | | Yes | 8 | | utf8mb4_latvian_ci | utf8mb4 | 226 | | Yes | 8 | | utf8mb4_romanian_ci | utf8mb4 | 227 | | Yes | 8 | | utf8mb4_slovenian_ci | utf8mb4 | 228 | | Yes | 8 | | utf8mb4_polish_ci | utf8mb4 | 229 | | Yes | 8 | | utf8mb4_estonian_ci | utf8mb4 | 230 | | Yes | 8 | | utf8mb4_spanish_ci | utf8mb4 | 231 | | Yes | 8 | | utf8mb4_swedish_ci | utf8mb4 | 232 | | Yes | 8 | | utf8mb4_turkish_ci | utf8mb4 | 233 | | Yes | 8 | | utf8mb4_czech_ci | utf8mb4 | 234 | | Yes | 8 | | utf8mb4_danish_ci | utf8mb4 | 235 | | Yes | 8 | | utf8mb4_lithuanian_ci | utf8mb4 | 236 | | Yes | 8 | | utf8mb4_slovak_ci | utf8mb4 | 237 | | Yes | 8 | | utf8mb4_spanish2_ci | utf8mb4 | 238 | | Yes | 8 | | utf8mb4_roman_ci | utf8mb4 | 239 | | Yes | 8 | | utf8mb4_persian_ci | utf8mb4 | 240 | | Yes | 8 | | utf8mb4_esperanto_ci | utf8mb4 | 241 | | Yes | 8 | | utf8mb4_hungarian_ci | utf8mb4 | 242 | | Yes | 8 | | utf8mb4_sinhala_ci | utf8mb4 | 243 | | Yes | 8 | | utf8mb4_german2_ci | utf8mb4 | 244 | | Yes | 8 | | utf8mb4_croatian_ci | utf8mb4 | 245 | | Yes | 8 | | utf8mb4_unicode_520_ci | utf8mb4 | 246 | | Yes | 8 | | utf8mb4_vietnamese_ci | utf8mb4 | 247 | | Yes | 8 | +------------------------+--------------------+-----+------------+-------------+---------+ 26 rows in set (0.11 sec)每个字符集都有一个默认的排序规则：IS_DEFAULT 为 Yes。
比较规则名称以与其关联的字符集的名称开头，可以用通过这个开头查询所有的字符集，也可以查询information_schema.collations精确指定字符集
字符集后面跟着的是语言编码，因为utf8mb4包含了所有字符，不同国家的文字语言排序肯定不一样。
最后末尾的ci代表case insensitive，大小写不敏感，所有可能的后缀如下所示：
ai: accent insensitive 不区分重音
as: accent sensitive 区分重音
ci: case insensitive 不区分大小写
cs: case sensitive 区分大小写
bin: binary 以二进制方式比较
应用字符集与比较规则字符集与比较规则配置有四个级别：
MySQL实例级别
库级别
表级别
字段级别
指定的级别粒度越小，则以粒度越小的字符集还有比较规则优先。例如指定MySQL实例级别字符集是utf8mb4，指定某个表字符集是latin1，那么这个表的所有字段如果不指定的话，编码就是latin1
由于字符集和比较规则是互相有联系的，如果我们只修改了字符集，比较规则也会跟着变化，如果只修改了比较规则，字符集也会跟着变化，具体规则如下：
只修改字符集，则比较规则将变为修改后的字符集默认的比较规则。
只修改比较规则，则字符集将变为修改后的比较规则对应的字符集。
实例级别通过两个系统变量来指定实例级别的字符集与排序规则。
配置文件：
[server] character_set_server=utf8mb4 collation_server=utf8mb4_general_ci启动之后，可以查看并修改这两个变量。
mysql> show variables like 'character_set_server'; +----------------------+---------+ | Variable_name | Value | +----------------------+---------+ | character_set_server | utf8mb4 | +----------------------+---------+ 1 row in set (0.06 sec) mysql> show variables like 'collation_server'; +------------------+--------------------+ | Variable_name | Value | +------------------+--------------------+ | collation_server | utf8mb4_general_ci | +------------------+--------------------+ 1 row in set (0.05 sec) mysql> set character_set_server = 'utf8mb4'; Query OK, 0 rows affected (0.00 sec) mysql> set collation_server = 'utf8mb4_general_ci'; Query OK, 0 rows affected (0.00 sec) 库级别创建数据库的时候，可以指定字符集还有排序规则。
mysql> create database test_db character set utf8mb4 collate utf8mb4_general_ci; Query OK, 1 row affected (0.01 sec)不指定的话，就用实例级别的字符集还有排序规则。
查看当前数据库的字符集还有排序规则则是通过use命令指定数据库之后，查看character_set_database变量以及collation_database 来实现：
mysql> show variables like 'character_set_database'; +------------------------+---------+ | Variable_name | Value | +------------------------+---------+ | character_set_database | utf8mb4 | +------------------------+---------+ 1 row in set (0.07 sec) mysql> show variables like 'collation_database'; +--------------------+--------------------+ | Variable_name | Value | +--------------------+--------------------+ | collation_database | utf8mb4_general_ci | +--------------------+--------------------+ 1 row in set (0.09 sec)