Mysql charset/collation字符编码设置
mysql在创建数据库时有两个跟字符编码相关的参数”character set”和”collate”，这里解释一下这两个参数的作用。
character set
“character set”很容易解释，就是指定字符在存储到mysql中时使用的编码集。数据库支持哪些编码可以通过”show character set”获得。
mysql> 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 |
+----------+-----------------------------+---------------------+--------+
40 rows in set (0.00 sec)
collate
这个参数指定mysql根据哪些规则来比较存储的数据的字符集，这些信息可以用来进行数据的比较排序。
这个参数的格式构成规则如下：
“<字符集>_<语言相关信息>_<后缀>”
例如： “utf8_general_ci”, “latin1_danish_ci”
mysql一些其他特性
1. mysql支持4个级别的字符集设置：服务器，数据库，表，列。
1.1 服务器级别
- 作用：
服务器的字符集可以作为”CREATE DATABASE”的默认值
- 设置方法：
启动参数： ‘–character-set-server’ ‘–collation-server’
- 查询：
SHOW VARIABLES 查询 character_set_server/collation_server
1.2 数据库级别
- 作用：
作为创建表时的默认值
影响LOAD_DATA语句中的CHARACTER SET的值
影响存储过程中与字符编码相关的操作
- 设置方法：
‘CREATE DATABASE’或’ALTER DATABASE’ 的参数 ‘CHARACTER SET’ ‘COLLATE’
- 查询：
USE db_name;SELECT @@character_set_database, @@collation_database;
1.3 表级别
- 作用：
每张表可以有表级别的字符集。
- 设置方法：
使用 CREATE TABLE 和 ALTER TABLE 命令进行设置。
CREATE TABLE tbl_name (column_list)
[[DEFAULT] CHARACTER SET charset_name]
[COLLATE collation_name]]
ALTER TABLE tbl_name
[[DEFAULT] CHARACTER SET charset_name]
[COLLATE collation_name]
- 查询：
SHOW CREATE TABLE table_name;
1.4 列级别
- 作用：
字符类型的列（CHAR, VARCHAR, TEXT）可以有一个本列相关的 character set和collation设置。
- 设置方法：
设置方法是在CREATE TABLE时使用相应的列参数。
col_name {CHAR | VARCHAR | TEXT} (col_length)
[CHARACTER SET charset_name]
[COLLATE collation_name]
比如：
CREATE TABLE t1
(
col1 VARCHAR(5)
CHARACTER SET utf8
COLLATE utf8_general_ci
);
ALTER TABLE t1 MODIFY
col1 VARCHAR(5)
CHARACTER SET utf8
COLLATE utf8_general_ci;
- 查询：
SHOW CREATE TABLE table_name;
client/server通讯字符编码
- 设置：
mysql数据库client/server之间通讯的字符编码也可以单独设置，设置的方法有若干种：
使用SQL命令”SET NAME ‘charset_name”和 “SET CHAARACTER SET ‘charset_name’“设置：
SET NAME 'utf8';
SET character_set_client = charset_name;
SET character_set_results = charset_name;
SET collation_connection = @@collation_database;
使用mysql配置文件设置：
[mysql] default-character-set=koi8r
使用mysql客户端设置：
mysql> charset utf8
Charset changed
- 查询：
SHOW VARIABLES LIKE 'character_set%';
SHOW VARIABLES LIKE 'collation%';
