标签：字符串 format cti cal class led files local efault
1）MySQL提供了多种字符集和排序规则选择，其中字符集设置和数据存储以及客户端与MySQL实例的交互相关，排序规则和字符串的对比规则相关
2）字符集的设置可以在MySQL实例、数据库、表、列四个级别
3）MySQL设置字符集支持在InnoDB, MyISAM, Memory三个存储引擎
4）查看当前MySQL支持的字符集的方式有两种，一种是通过查看information_schema.character_sets系统表，一种是通过命令show character set查看
mysql> select * from information_schema.character_sets; 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 | #常用 | 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 | +----------+---------------------------------+---------------------+--------+
5）每个指定的字符集都会有一个或多个支持的排序规则，可以通过两种方式查看，一种是查看information_schema.collations表，另一种是通过show collation命令查看
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 | +-------------------+---------+----+---------+----------+---------+
6）每个字符集可以对应多个排序规则，但每个排序规则只能对应一个字符集，例如下面的对应关系会报错
mysql> SELECT _latin1 ‘x‘ COLLATE latin2_bin; ERROR 1253 (42000): COLLATION ‘latin2_bin‘ is not valid for CHARACTER SET ‘latin1‘
1）排序规则的命令通常是以对应的字符集的名字为开头，并以自己的特定属性结尾，比如排序规则utf8_general_ci和latin1_swedish_ci就分别是对应utf8和latin1字符集的排序规则
2）当排序规则特指某种语言时，则中间的部分就为这种语言的名字，比如utf8_turkish_ci和utf8_hungarian_ci就代表UTF8字符集中的土耳其语和匈牙利语
3）排序规则名字的结尾字符代表是否大小写敏感，重音敏感以及是否是二进制的
4）当排序规则名字中没有指定_as或者_ai时，则是否口音敏感是由_ci或者_cs决定，当使用的是_ci是则暗指_ai，反之则暗指_as。比如latin1_general_ci显示指定大小写不敏感，也暗指口音不敏感, 而latin1_general_cs显示指定大小写敏感，也暗指口音敏感
5）对Unicode的字符集来说，对应的排序规则也可能会包含unicode排序算法的版本号，如果没有这个版本号显示则表示是基于4.0.0这个版本，比如utf8_unicode_520_ci和utf8_unicode_ci
#默认情况下的字符集是latin1
mysql> show variables like ‘%character%‘;
+--------------------------+----------------------------------+
| Variable_name | Value |
+--------------------------+----------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/local/mysql/share/charsets/ |
+--------------------------+----------------------------------+
#在Latin1下创建的表默认字符集也是Latin1
mysql> create database chartest;
mysql> show create database chartest;
+----------+---------------------------------------------------------------------+
| Database | Create Database |
+----------+---------------------------------------------------------------------+
| chartest | CREATE DATABASE `chartest` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+---------------------------------------------------------------------+
mysql> create table temp(name varchar(100),name2 varchar(100));
mysql> show create table temp\G
*************************** 1. row ***************************
Table: temp
Create Table: CREATE TABLE `temp` (
`name` varchar(100) DEFAULT NULL,
`name2` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin11）ASCII码(American Standard Code for Information Interchange，美国信息交换标准代码）是基于拉丁字母的一套电脑编码系统。它主要用于显示现代英语
2）ASCII的局限在于只能显示26个基本拉丁字母、阿拉伯数目字和英式标点符号，因此只能用于显示现代美国英语（而且在处理英语当中的外来词如na?ve、café、élite等等时，所有重音符号都不得不去掉，即使这样做会违反拼写规则）
标签：字符串 format cti cal class led files local efault
原文地址：https://www.cnblogs.com/hujinzhong/p/11640819.html
