--- title: 关于 OceanBase 数据库字符集和字符序的说明-OceanBase数据库使用指南 description: 了解OceanBase数据库在实际应用中关于关于 OceanBase 数据库字符集和字符序的说明相关的常见问题和使用技巧，帮助您快速解决关于 OceanBase 数据库字符集和字符序的说明的难题。 image: https://mdn.alipayobjects.com/huamei_22khvb/afts/img/A*OSPzQ6GUQF4AAAAAQHAAAAgAeiGDAQ/original --- 切换语言 - 中文站 - 简体中文 - International - English - 日本站 - 日本語 划线反馈 # 关于 OceanBase 数据库字符集和字符序的说明 更新时间：2026-08-14 07:01 适用版本： V2.1.x、V2.2.x、V3.1.x、V3.2.x、V4.0.x、V4.1.x、V4.2.x、V4.3.x、V4.4.x 内容类型：TechNote OceanBase 数据库支持多种字符集和字符序，允许你根据实际需要存储各种语言文字，并控制字符串的比较和排序规则。 - **字符集（Character Set）：** 定义了字符的编码规则，决定了数据库能存储哪些字符。例如，`utf8mb4` 可以存储包括表情符号在内的绝大多数 `Unicode` 字符。 - **字符序（Collation）：** 定义了同一字符集内字符的比较、排序规则。例如，在 `utf8mb4` 字符集下。 - `utf8mb4_bin` 会严格区分大小写。 - `utf8mb4_general_ci` 则不区分大小写（`ci` 表示 `Case Insensitive`）。 本文主要介绍了 OceanBase 数据库字符集和字符序的基本知识和常见用法。 ## 详细说明 1. 查看当前版本的租户支持的字符集和字符序。 ```shell -- MySQL 模式和 Oracle 模式下均支持 show charset; -- 查看当前版本租户支持的所有字符集 show collation; -- 查看当前版本租户支持的所有字符序 ``` 例如在 OceanBase 数据库 V4.2.5 版本中，支持如下种类的字符集和字符序： ```sql obclient> show charset; +--------------+-----------------------+-------------------------+--------+ | CHARSET | DESCRIPTION | DEFAULT COLLATION | MAXLEN | +--------------+-----------------------+-------------------------+--------+ | binary | Binary pseudo charset | binary | 1 | | utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 | | gbk | GBK charset | gbk_chinese_ci | 2 | | utf16 | UTF-16 Unicode | utf16_general_ci | 4 | | gb18030 | GB18030 charset | gb18030_chinese_ci | 4 | | latin1 | cp1252 West European | latin1_swedish_ci | 1 | | gb18030_2022 | GB18030-2022 charset | gb18030_2022_chinese_ci | 4 | | ascii | US ASCII | ascii_general_ci | 1 | | tis620 | TIS620 Thai | tis620_thai_ci | 1 | | utf16le | UTF-16LE Unicode | utf16le_general_ci | 4 | | sjis | SJIS | sjis_japanese_ci | 2 | | big5 | BIG5 | big5_chinese_ci | 2 | | hkscs | HKSCS | hkscs_bin | 2 | | hkscs31 | HKSCS-ISO UNICODE 31 | hkscs31_bin | 2 | | dec8 | DEC West European | dec8_swedish_ci | 1 | +--------------+-----------------------+-------------------------+--------+ 15 rows in set (0.004 sec) obclient> show collation; +----------------------------+--------------+------+---------+----------+---------+ | COLLATION | CHARSET | ID | DEFAULT | COMPILED | SORTLEN | +----------------------------+--------------+------+---------+----------+---------+ | utf8mb4_general_ci | utf8mb4 | 45 | Yes | Yes | 1 | | utf8mb4_bin | utf8mb4 | 46 | NULL | Yes | 1 | | binary | binary | 63 | Yes | Yes | 1 | | gbk_chinese_ci | gbk | 28 | Yes | Yes | 1 | | gbk_bin | gbk | 87 | NULL | Yes | 1 | | utf16_general_ci | utf16 | 54 | Yes | Yes | 1 | | utf16_bin | utf16 | 55 | NULL | Yes | 1 | | gb18030_chinese_ci | gb18030 | 248 | Yes | Yes | 2 | | gb18030_bin | gb18030 | 249 | NULL | Yes | 1 | | latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 | | latin1_german1_ci | latin1 | 5 | NULL | Yes | 1 | | latin1_danish_ci | latin1 | 15 | NULL | Yes | 1 | | latin1_german2_ci | latin1 | 31 | NULL | Yes | 1 | | latin1_general_ci | latin1 | 48 | NULL | Yes | 1 | | latin1_general_cs | latin1 | 49 | NULL | Yes | 1 | | latin1_spanish_ci | latin1 | 94 | NULL | Yes | 1 | | latin1_bin | latin1 | 47 | NULL | Yes | 1 | | gb18030_2022_bin | gb18030_2022 | 216 | NULL | Yes | 1 | | gb18030_2022_chinese_ci | gb18030_2022 | 217 | Yes | Yes | 1 | | gb18030_2022_chinese_cs | gb18030_2022 | 218 | NULL | Yes | 1 | | gb18030_2022_radical_ci | gb18030_2022 | 219 | NULL | Yes | 1 | | gb18030_2022_radical_cs | gb18030_2022 | 220 | NULL | Yes | 1 | | gb18030_2022_stroke_ci | gb18030_2022 | 221 | NULL | Yes | 1 | | gb18030_2022_stroke_cs | gb18030_2022 | 222 | NULL | Yes | 1 | | ascii_general_ci | ascii | 11 | Yes | Yes | 1 | | ascii_bin | ascii | 65 | NULL | Yes | 1 | | tis620_thai_ci | tis620 | 18 | Yes | Yes | 1 | | tis620_bin | tis620 | 89 | NULL | Yes | 1 | | utf16le_general_ci | utf16le | 56 | Yes | Yes | 1 | | utf16le_bin | utf16le | 62 | NULL | Yes | 1 | | sjis_japanese_ci | sjis | 13 | Yes | Yes | 1 | | sjis_bin | sjis | 88 | NULL | Yes | 1 | | big5_chinese_ci | big5 | 1 | Yes | Yes | 1 | | big5_bin | big5 | 84 | NULL | Yes | 1 | | hkscs_bin | hkscs | 152 | Yes | Yes | 1 | | hkscs31_bin | hkscs31 | 153 | Yes | Yes | 1 | | utf16_unicode_ci | utf16 | 101 | NULL | Yes | 8 | | utf16_icelandic_ci | utf16 | 102 | NULL | Yes | 8 | | utf16_latvian_ci | utf16 | 103 | NULL | Yes | 8 | | utf16_romanian_ci | utf16 | 104 | NULL | Yes | 8 | | utf16_slovenian_ci | utf16 | 105 | NULL | Yes | 8 | | utf16_polish_ci | utf16 | 106 | NULL | Yes | 8 | | utf16_estonian_ci | utf16 | 107 | NULL | Yes | 8 | | utf16_spanish_ci | utf16 | 108 | NULL | Yes | 8 | | utf16_swedish_ci | utf16 | 109 | NULL | Yes | 8 | | utf16_turkish_ci | utf16 | 110 | NULL | Yes | 8 | | utf16_czech_ci | utf16 | 111 | NULL | Yes | 8 | | utf16_danish_ci | utf16 | 112 | NULL | Yes | 8 | | utf16_lithuanian_ci | utf16 | 113 | NULL | Yes | 8 | | utf16_slovak_ci | utf16 | 114 | NULL | Yes | 8 | | utf16_spanish2_ci | utf16 | 115 | NULL | Yes | 8 | | utf16_roman_ci | utf16 | 116 | NULL | Yes | 8 | | utf16_persian_ci | utf16 | 117 | NULL | Yes | 8 | | utf16_esperanto_ci | utf16 | 118 | NULL | Yes | 8 | | utf16_hungarian_ci | utf16 | 119 | NULL | Yes | 8 | | utf16_sinhala_ci | utf16 | 120 | NULL | Yes | 8 | | utf16_german2_ci | utf16 | 121 | NULL | Yes | 8 | | utf16_croatian_ci | utf16 | 122 | NULL | Yes | 8 | | utf16_unicode_520_ci | utf16 | 123 | NULL | Yes | 8 | | utf16_vietnamese_ci | utf16 | 124 | NULL | Yes | 8 | | utf8mb4_unicode_ci | utf8mb4 | 224 | NULL | Yes | 8 | | utf8mb4_icelandic_ci | utf8mb4 | 225 | NULL | Yes | 8 | | utf8mb4_latvian_ci | utf8mb4 | 226 | NULL | Yes | 8 | | utf8mb4_romanian_ci | utf8mb4 | 227 | NULL | Yes | 8 | | utf8mb4_slovenian_ci | utf8mb4 | 228 | NULL | Yes | 8 | | utf8mb4_polish_ci | utf8mb4 | 229 | NULL | Yes | 8 | | utf8mb4_estonian_ci | utf8mb4 | 230 | NULL | Yes | 8 | | utf8mb4_spanish_ci | utf8mb4 | 231 | NULL | Yes | 8 | | utf8mb4_swedish_ci | utf8mb4 | 232 | NULL | Yes | 8 | | utf8mb4_turkish_ci | utf8mb4 | 233 | NULL | Yes | 8 | | utf8mb4_czech_ci | utf8mb4 | 234 | NULL | Yes | 8 | | utf8mb4_danish_ci | utf8mb4 | 235 | NULL | Yes | 8 | | utf8mb4_lithuanian_ci | utf8mb4 | 236 | NULL | Yes | 8 | | utf8mb4_slovak_ci | utf8mb4 | 237 | NULL | Yes | 8 | | utf8mb4_spanish2_ci | utf8mb4 | 238 | NULL | Yes | 8 | | utf8mb4_roman_ci | utf8mb4 | 239 | NULL | Yes | 8 | | utf8mb4_persian_ci | utf8mb4 | 240 | NULL | Yes | 8 | | utf8mb4_esperanto_ci | utf8mb4 | 241 | NULL | Yes | 8 | | utf8mb4_hungarian_ci | utf8mb4 | 242 | NULL | Yes | 8 | | utf8mb4_sinhala_ci | utf8mb4 | 243 | NULL | Yes | 8 | | utf8mb4_german2_ci | utf8mb4 | 244 | NULL | Yes | 8 | | utf8mb4_croatian_ci | utf8mb4 | 245 | NULL | Yes | 8 | | utf8mb4_unicode_520_ci | utf8mb4 | 246 | NULL | Yes | 8 | | utf8mb4_vietnamese_ci | utf8mb4 | 247 | NULL | Yes | 8 | | dec8_swedish_ci | dec8 | 3 | Yes | Yes | 8 | | dec8_bin | dec8 | 69 | NULL | Yes | 8 | | utf8mb4_0900_ai_ci | utf8mb4 | 255 | NULL | Yes | 0 | | utf8mb4_de_pb_0900_ai_ci | utf8mb4 | 256 | NULL | Yes | 0 | | utf8mb4_is_0900_ai_ci | utf8mb4 | 257 | NULL | Yes | 0 | | utf8mb4_lv_0900_ai_ci | utf8mb4 | 258 | NULL | Yes | 0 | | utf8mb4_ro_0900_ai_ci | utf8mb4 | 259 | NULL | Yes | 0 | | utf8mb4_sl_0900_ai_ci | utf8mb4 | 260 | NULL | Yes | 0 | | utf8mb4_pl_0900_ai_ci | utf8mb4 | 261 | NULL | Yes | 0 | | utf8mb4_et_0900_ai_ci | utf8mb4 | 262 | NULL | Yes | 0 | | utf8mb4_es_0900_ai_ci | utf8mb4 | 263 | NULL | Yes | 0 | | utf8mb4_sv_0900_ai_ci | utf8mb4 | 264 | NULL | Yes | 0 | | utf8mb4_tr_0900_ai_ci | utf8mb4 | 265 | NULL | Yes | 0 | | utf8mb4_cs_0900_ai_ci | utf8mb4 | 266 | NULL | Yes | 0 | | utf8mb4_da_0900_ai_ci | utf8mb4 | 267 | NULL | Yes | 0 | | utf8mb4_lt_0900_ai_ci | utf8mb4 | 268 | NULL | Yes | 0 | | utf8mb4_sk_0900_ai_ci | utf8mb4 | 269 | NULL | Yes | 0 | | utf8mb4_es_trad_0900_ai_ci | utf8mb4 | 270 | NULL | Yes | 0 | | utf8mb4_la_0900_ai_ci | utf8mb4 | 271 | NULL | Yes | 0 | | utf8mb4_eo_0900_ai_ci | utf8mb4 | 273 | NULL | Yes | 0 | | utf8mb4_hu_0900_ai_ci | utf8mb4 | 274 | NULL | Yes | 0 | | utf8mb4_hr_0900_ai_ci | utf8mb4 | 275 | NULL | Yes | 0 | | utf8mb4_vi_0900_ai_ci | utf8mb4 | 277 | NULL | Yes | 0 | | utf8mb4_0900_as_cs | utf8mb4 | 278 | NULL | Yes | 0 | | utf8mb4_de_pb_0900_as_cs | utf8mb4 | 279 | NULL | Yes | 0 | | utf8mb4_is_0900_as_cs | utf8mb4 | 280 | NULL | Yes | 0 | | utf8mb4_lv_0900_as_cs | utf8mb4 | 281 | NULL | Yes | 0 | | utf8mb4_ro_0900_as_cs | utf8mb4 | 282 | NULL | Yes | 0 | | utf8mb4_sl_0900_as_cs | utf8mb4 | 283 | NULL | Yes | 0 | | utf8mb4_pl_0900_as_cs | utf8mb4 | 284 | NULL | Yes | 0 | | utf8mb4_et_0900_as_cs | utf8mb4 | 285 | NULL | Yes | 0 | | utf8mb4_es_0900_as_cs | utf8mb4 | 286 | NULL | Yes | 0 | | utf8mb4_sv_0900_as_cs | utf8mb4 | 287 | NULL | Yes | 0 | | utf8mb4_tr_0900_as_cs | utf8mb4 | 288 | NULL | Yes | 0 | | utf8mb4_cs_0900_as_cs | utf8mb4 | 289 | NULL | Yes | 0 | | utf8mb4_da_0900_as_cs | utf8mb4 | 290 | NULL | Yes | 0 | | utf8mb4_lt_0900_as_cs | utf8mb4 | 291 | NULL | Yes | 0 | | utf8mb4_sk_0900_as_cs | utf8mb4 | 292 | NULL | Yes | 0 | | utf8mb4_es_trad_0900_as_cs | utf8mb4 | 293 | NULL | Yes | 0 | | utf8mb4_la_0900_as_cs | utf8mb4 | 294 | NULL | Yes | 0 | | utf8mb4_eo_0900_as_cs | utf8mb4 | 296 | NULL | Yes | 0 | | utf8mb4_hu_0900_as_cs | utf8mb4 | 297 | NULL | Yes | 0 | | utf8mb4_hr_0900_as_cs | utf8mb4 | 298 | NULL | Yes | 0 | | utf8mb4_vi_0900_as_cs | utf8mb4 | 300 | NULL | Yes | 0 | | utf8mb4_ja_0900_as_cs | utf8mb4 | 303 | NULL | Yes | 0 | | utf8mb4_ja_0900_as_cs_ks | utf8mb4 | 304 | NULL | Yes | 24 | | utf8mb4_0900_as_ci | utf8mb4 | 305 | NULL | Yes | 0 | | utf8mb4_ru_0900_ai_ci | utf8mb4 | 306 | NULL | Yes | 0 | | utf8mb4_ru_0900_as_cs | utf8mb4 | 307 | NULL | Yes | 0 | | utf8mb4_zh_0900_as_cs | utf8mb4 | 308 | NULL | Yes | 0 | | utf8mb4_0900_bin | utf8mb4 | 309 | NULL | Yes | 1 | | utf8mb4_nb_0900_ai_ci | utf8mb4 | 310 | NULL | Yes | 0 | | utf8mb4_nb_0900_as_cs | utf8mb4 | 311 | NULL | Yes | 0 | | utf8mb4_nn_0900_ai_ci | utf8mb4 | 312 | NULL | Yes | 0 | | utf8mb4_nn_0900_as_cs | utf8mb4 | 313 | NULL | Yes | 0 | | utf8mb4_sr_latn_0900_ai_ci | utf8mb4 | 314 | NULL | Yes | 0 | | utf8mb4_sr_latn_0900_as_cs | utf8mb4 | 315 | NULL | Yes | 0 | | utf8mb4_bs_0900_ai_ci | utf8mb4 | 316 | NULL | Yes | 0 | | utf8mb4_bs_0900_as_cs | utf8mb4 | 317 | NULL | Yes | 0 | | utf8mb4_bg_0900_ai_ci | utf8mb4 | 318 | NULL | Yes | 0 | | utf8mb4_bg_0900_as_cs | utf8mb4 | 319 | NULL | Yes | 0 | | utf8mb4_gl_0900_ai_ci | utf8mb4 | 320 | NULL | Yes | 0 | | utf8mb4_gl_0900_as_cs | utf8mb4 | 321 | NULL | Yes | 0 | | utf8mb4_mn_cyrl_0900_ai_ci | utf8mb4 | 322 | NULL | Yes | 0 | | utf8mb4_mn_cyrl_0900_as_cs | utf8mb4 | 323 | NULL | Yes | 0 | +----------------------------+--------------+------+---------+----------+---------+ 149 rows in set (0.003 sec) ``` 需要注意某个具体的字符集跟它支持的字符序是强相关的： ```sql obclient> show collation where charset like 'gbk'; +----------------+---------+------+---------+----------+---------+ | COLLATION | CHARSET | ID | DEFAULT | COMPILED | SORTLEN | +----------------+---------+------+---------+----------+---------+ | gbk_chinese_ci | gbk | 28 | Yes | Yes | 1 | | gbk_bin | gbk | 87 | NULL | Yes | 1 | +----------------+---------+------+---------+----------+---------+ 2 rows in set (0.004 sec) obclient> show collation where charset like 'latin1'; +-------------------+---------+------+---------+----------+---------+ | COLLATION | CHARSET | ID | DEFAULT | COMPILED | SORTLEN | +-------------------+---------+------+---------+----------+---------+ | latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 | | latin1_german1_ci | latin1 | 5 | NULL | Yes | 1 | | latin1_danish_ci | latin1 | 15 | NULL | Yes | 1 | | latin1_german2_ci | latin1 | 31 | NULL | Yes | 1 | | latin1_general_ci | latin1 | 48 | NULL | Yes | 1 | | latin1_general_cs | latin1 | 49 | NULL | Yes | 1 | | latin1_spanish_ci | latin1 | 94 | NULL | Yes | 1 | | latin1_bin | latin1 | 47 | NULL | Yes | 1 | +-------------------+---------+------+---------+----------+---------+ 8 rows in set (0.005 sec) ``` 2. 创建业务租户时支持指定该租户的字符集（可选）和字符序（可选）。 示例如下： ```sql CREATE TENANT IF NOT EXISTS test_tenant PRIMARY_ZONE='zone1;zone2,zone3', RESOURCE_POOL_LIST=('pool1'), CHARSET='utf8mb4' SET ob_tcp_invited_nodes TO '%'; create tenant tenant_mysql replica_num = 1, resource_pool_list = ('mysql_pool'), charset = ut8mb4, collate = utf8mb4_bin set ob_tcp_invited_nodes='%', ob_compatibility_mode='mysql'; CREATE TENANT tenant_charset_test REPLICA_NUM = 1, RESOURCE_POOL_LIST = ('pool_charset_test'), charset = 'gbk', set ob_tcp_invited_nodes='%', ob_compatibility_mode='oracle'; ``` #### 注意 从 OceanBase 数据库 V2.2.x 版本开始，创建 Oracle 租户时仅支持设置租户的字符集，不支持设置字符序，系统会使用所配置字符集的默认字符序。 3. 查看当前业务租户的字符集和字符序。 - MySQL 模式租户。 ```sql MySQL [(none)]> show variables like '%character%'; +--------------------------+---------+ | Variable_name | Value | +--------------------------+---------+ | character_set_client | utf8mb4 | | character_set_connection | utf8mb4 | <== 常量使用的字符集 | character_set_database | utf8mb4 | <== 对应租户的字符集 | character_set_filesystem | binary | | character_set_results | utf8mb4 | <== The character set which server should translate to before shipping result sets or error message back to the client | character_set_server | utf8mb4 | | character_set_system | utf8mb4 | +--------------------------+---------+ 7 rows in set (0.00 sec) MySQL [(none)]> show global variables like '%coll%'; +-------------------------------+--------------------+ | Variable_name | Value | +-------------------------------+--------------------+ | collation_connection | utf8mb4_general_ci | <== 常量使用的字符序 | collation_database | utf8mb4_general_ci | <== 创建 database 时候默认的字符序 | collation_server | utf8mb4_general_ci | <== 修改 collation_server 不会影响已经创建的表 | default_collation_for_utf8mb4 | utf8mb4_general_ci | +-------------------------------+--------------------+ 4 rows in set (0.00 sec) ``` - Oracle 模式租户。 ```sql obclient [SYS]> SELECT value FROM v$nls_parameters WHERE parameter='NLS_CHARACTERSET'; +----------+ | VALUE | +----------+ | AL32UTF8 | +----------+ 1 row in set (0.001 sec) obclient [SYS]> show global variables like '%nls%'; +-------------------------+------------------------------+ | VARIABLE_NAME | VALUE | +-------------------------+------------------------------+ | nls_calendar | GREGORIAN | | nls_characterset | AL32UTF8 | <== Oracle 租户的字符集 | nls_comp | BINARY | | nls_currency | $ | | nls_date_format | DD-MON-RR | | nls_date_language | AMERICAN | | nls_dual_currency | $ | | nls_iso_currency | AMERICA | | nls_length_semantics | BYTE | | nls_nchar_characterset | AL16UTF16 | | nls_nchar_conv_excp | FALSE | | nls_numeric_characters | ., | | nls_sort | BINARY | | nls_territory | AMERICA | | nls_timestamp_format | DD-MON-RR HH.MI.SSXFF AM | | nls_timestamp_tz_format | DD-MON-RR HH.MI.SSXFF AM TZR | +-------------------------+------------------------------+ 16 rows in set (0.002 sec) obclient [SYS]> show global variables like '%coll%'; +----------------------+-------------+ | VARIABLE_NAME | VALUE | +----------------------+-------------+ | collation_connection | utf8mb4_bin | <== 常量使用的字符序 +----------------------+-------------+ 1 row in set (0.004 sec) obclient [SYS]> select unique collation from dba_ob_databases; +-------------+ | COLLATION | +-------------+ | utf8mb4_bin | <== Oracle 租户下所有 schema 的字符序均一致，不支持单独设置 +-------------+ 1 row in set (0.001 sec) ``` 4. 租户一旦创建好之后不支持修改租户级别的字符集和字符序。 ```sql MySQL [oceanbase]> alter tenant mysqlt charset=gbk; ERROR 1235 (0A000): tenant change charset not supported MySQL [oceanbase]> alter tenant oraclet charset=gbk; ERROR 1235 (0A000): tenant change charset not supported MySQL [oceanbase]> alter tenant mysqlt collate=utf8mb4_bin; ERROR 1235 (0A000): tenant change collation not supported MySQL [oceanbase]> alter tenant oraclet collate=utf8mb4_bin; ERROR 1235 (0A000): tenant change collation not supported ``` 5. Oracle 租户只支持设置租户级别的字符集。 **OceanBase 数据库 Oracle 租户不支持为 user、database、table 或 column 单独设置字符集或字符序，只支持设置租户级别的字符集，跟原生的 Oracle 保持一致（原生 Oracle 不支持指定表的字符集。在原生 Oracle 数据库中，字符集是在数据库级别设置的，而不是针对单个表进行设置的）**。 ```sql obclient [SYS]> create table t1 (name varchar(10) charset gbk); ORA-00600: internal error code, arguments: -4007, set charset in oracle mode not supported ``` 6. MySQL 租户支持设置和修改 database/table/column 级别的字符集和字符序。 #### 注意 OceanBase 数据库 V2.x/V3.x 中 MySQL 租户只支持修改 database 的字符集/字符序。 - 创建时指定字符集、字符序。 ```sql MySQL [(none)]> create database db1 character set 'utf8mb4'; MySQL [(none)]> create database db2 character set 'gbk' collate 'gbk_bin'; MySQL [test]> create table nocase (name varchar(100) primary key) charset=utf8mb4 collate=utf8mb4_bin; MySQL [test]> create table t1 (name varchar(10) charset gbk); MySQL [test]> create table t2 (name varchar(100)) collate=utf8mb4_unicode_ci; ``` - 修改数据库的字符集、字符序。 ```sql MySQL [(none)]> alter database test character set 'utf8mb4'; MySQL [(none)]> alter database test character set 'utf8mb4' collate 'utf8mb4_bin'; MySQL [(none)]> alter database lower_db character set 'utf8mb4' collate 'utf8mb4_bin'; MySQL [(none)]> alter database test character set 'utf8mb4' collate 'utf8mb4_bin'; MySQL [(none)]> ALTER DATABASE test2 DEFAULT CHARACTER SET utf8mb4; MySQL [(none)]> ALTER DATABASE test2 DEFAULT COLLATE utf8mb4_bin; ``` #### 注意 变更数据库的 charset/collation 不会影响现有表的 charset/collation，只会影响后续新建表的 charset/collation，因为存量表、列的 charset/collations 都已经持久化到 `oceanbase.__all_table`、`oceanbase.__all_column` 中去了。变更表的 charset/collation 时情况类似。 - OceanBase 数据库 V4.x 中支持修改某张表的字符集、字符序（OceanBase 数据库 V2.x/V3.x 中不支持）。 ```sql MySQL [test]> alter table nocase collate=utf8mb4_bin; MySQL [test]> alter table t1 collate=utf8mb4_bin; ``` - OceanBase 数据库 V4.x 中支持修改某列的字符集、字符序（OceanBase 数据库 V2.x/V3.x 中不支持）。 ```sql MySQL [test]> alter table nocase modify name varchar(100) collate utf8mb4_bin; ``` 7. MySQL 租户下 database/table/column 级别字符集和字符序的优先级。 MySQL 租户下 database/table/column 级别字符集和字符序的优先级如下：**租户级别的设置 < database 级别的设置 < table 级别的设置 < column 级别的设置 < create、alter 语句中指定的字符集和字符序**。 具体如下： - 对 database 而言，如果创建时指定了字符集/字符序，以实际指定的为准；如果未指定，则自动继承所属租户的字符集/字符序。 - 对 table 而言，如果创建时指定了字符集/字符序，以实际指定的为准；如果未指定，则自动继承所属 database 的字符集/字符序。 - 对 column 而言，如果创建时指定了字符集/字符序，以实际指定的为准；如果未指定，则自动继承所属 table 的字符集/字符序。 - **变更数据库的 charset/collation 不会影响现有表的 charset/collation，只会影响后续新建表的 charset/collation，因为存量表、列的 charset/collations 都已经持久化到 `oceanbase.__all_table`、`oceanbase.__all_column` 中去了。变更表的 charset/collation 时情况类似**。 8. 同一字符集下不同的字符序会影响字符串比较的结果。 以点号（`.`）和下划线（`_`）为例，如果采用 `utf8mb4` 字符集默认的字符序 `utf8mb4_general_ci`，则点号（`.`）< 下划线（`_`）；如果采用 `utf8mb4_unicode_ci` 进行比较，则点号（`.`）> 下划线（`_`）： ```sql -- 在 OceanBase 数据库 MySQL 中 MySQL [test]> SELECT '.' AS char1, '_' AS char2, CASE WHEN '.' < '_' COLLATE "utf8mb4_general_ci" THEN 'char1 < char2' WHEN '.' > '_' COLLATE "utf8mb4_general_ci" THEN 'char1 > char2' ELSE 'char1 = char2' END AS comparison_result_en_us; +-------+-------+-------------------------+ | char1 | char2 | comparison_result_en_us | +-------+-------+-------------------------+ | . | _ | char1 < char2 | +-------+-------+-------------------------+ 1 row in set (0.001 sec) MySQL [test]> SELECT '.' AS char1, '_' AS char2, CASE WHEN '.' < '_' COLLATE "utf8mb4_unicode_ci" THEN 'char1 < char2' WHEN '.' > '_' COLLATE "utf8mb4_unicode_ci" THEN 'char1 > char2' ELSE 'char1 = char2' END AS comparison_result_en_us; +-------+-------+-------------------------+ | char1 | char2 | comparison_result_en_us | +-------+-------+-------------------------+ | . | _ | char1 > char2 | +-------+-------+-------------------------+ 1 row in set (0.005 sec) MySQL [test]> select ascii('.'), ascii('_'); +------------+------------+ | ascii('.') | ascii('_') | +------------+------------+ | 46 | 95 | +------------+------------+ 1 row in set (0.001 sec) ``` ## 适用版本 OceanBase 数据库 V2.x/V3.x/V4.x 版本。 上一篇 [OBClient - source 导入数据报错：ERROR 1366 (HY000): Incorrect string value](https://www.oceanbase.com/knowledge-base/oceanbase-database-1000000001146738) 下一篇 [原生 Oracle 数据库迁移到 OceanBase 数据库 MySQL 模式租户中存在 TIMESTAMP 精度问题的原因和解决方法](https://www.oceanbase.com/knowledge-base/oceanbase-database-1000000003708068) ![有帮助](https://gw.alipayobjects.com/mdn/ob_asset/afts/img/A*y6ocSqN8cqsAAAAAAAAAAAAAARQnAQ)![无帮助](https://gw.alipayobjects.com/mdn/ob_asset/afts/img/A*BG9IQJyLHF8AAAAAAAAAAAAAARQnAQ)![反馈](https://gw.alipayobjects.com/mdn/ob_asset/afts/img/A*eTWdQKCRKHwAAAAAAAAAAAAAARQnAQ)[AI](https://www.oceanbase.com/obi) 咨询热线