mysql 字符集研究

 一、创建一个测试数据库 及一个测试用的表。均使用默认的编码方式。

   show variables like 'char%':

mysql> show variables like 'char%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | latin1                     |
| character_set_connection | latin1                     |
| character_set_database   | latin1                     |
| character_set_filesystem | binary                     |
| character_set_results    | latin1                     |
| character_set_server     | latin1                     |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

 　  create database dbtest

　　create table utf8Latin1Table(column_utf8 varchar(30),column_latin1 varchar(30));

  查看库及表的编码方式：均为 latin1 

mysql> show create database dbtest;
+----------+-------------------------------------------------------------------+
| Database | Create Database                                                   |
+----------+-------------------------------------------------------------------+
| dbtest   | CREATE DATABASE `dbtest` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> show create table test;
+-------+---------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                    |
+-------+---------------------------------------------------------------------------------------------------------------------------------+
| test  | CREATE TABLE `test` (
  `id` varchar(10) DEFAULT NULL,
  `name` varchar(30) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1 |
+-------+---------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

查看表中字段的编码：

mysql> show full columns from utf8Latin1Table;
+---------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
| Field         | Type        | Collation         | Null | Key | Default | Extra | Privileges                      | Comment |
+---------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
| column_utf8   | varchar(30) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
| column_latin1 | varchar(30) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         |
+---------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
2 rows in set (0.00 sec)

 修改column_utf8 的编码方式 ：由latin1 ------ utf8 形式

　　alter table utf8Latin1Table change column_utf8 column_utf8 varchar(30) character set utf8; 

　修改完字段的字符集后：　

mysql> show full columns from utf8Latin1Table;
+---------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
| Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment |
+---------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
| column_utf8 | varchar(30) | utf8_general_ci | YES | | NULL | | select,insert,update,references | |
| column_latin1 | varchar(30) | latin1_swedish_ci | YES | | NULL | | select,insert,update,references | |
+---------------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+

二、 向数据库中存入测试数据。（数据库连接工具是 UTF8 编码方式）

   测试 数据为 带重音的 e ：  é

  é 在 latin1中的编码为：E9   在utf8字符集中编码为：C3A9

mysql> insert into utf8Latin1Table values('é','é');
Query OK, 1 row affected (0.00 sec)

mysql> select * from utf8Latin1Table;
+-------------+---------------+
| column_utf8 | column_latin1 |
+-------------+---------------+
| é          | é            |
+-------------+---------------+
1 row in set (0.00 sec)

查看存储的二进制内容：

mysql> select hex(column_utf8),column_utf8,hex(column_latin1),column_latin1  from utf8Latin1Table;
+------------------+-------------+--------------------+---------------+
| hex(column_utf8) | column_utf8 | hex(column_latin1) | column_latin1 |
+------------------+-------------+--------------------+---------------+
| C383C2A9         | é          | C3A9               | é            |
+------------------+-------------+--------------------+---------------+
1 row in set (0.00 sec)

虽然存入的是一样的字符，但是存入的二进制信息不同。

三、分析Insert过程 、select 过程（未写）

涉及应用程序段字符编码（数据库查询工具，网页端等等），character_set_client ，character_set_connection，character_set_results ，及数据库编码（列编码）

    insert 过程：