怎么修改mysql的字符集和默認存儲引擎

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修改mysql的字符集和默認存儲引擎
 
1.修改mysql的字符集
mysql庫現有字符集
mysql> show variables like 'character%';
+--------------------------+----------------------------+
| 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)  www.2cto.com  
mysql>
mysql的字符集分為幾類
A.客戶端字符集：通過系統變量”character_set_client“表示，通知server端，客戶端提交的sql語句編碼格式
B.連接字符集：通過系統變量”character_set_connectiont“表示，server端翻譯sql語句時，使用的編碼格式
C.結果集字符集：通過系統變量”character_set_results“表示，server端返回結果集之前把結果集轉換成的編碼格式
D.存儲字符集：通過系統變量”character_set_results“和“character_set_server”表示，是數據在存儲引擎里編碼格式
 
為了不出現亂碼，我們需要統一修改這些參數，比如我要把的默認字符集改為utf8，如下所示
在[client]下添加如下參數
default-character-set=utf8
在[d]下添加如下參數
default-character-set=utf8
然后重啟mysql服務，再查看字符集（要重新登錄客戶端）
  www.2cto.com  
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     | utf8                       | 
| character_set_system     | utf8                       | 
| character_sets_dir       | /usr/share/mysql/charsets/ | 
+--------------------------+----------------------------+
8 rows in set (0.01 sec)
mysql>
mysql> show variables like 'collation%';
+----------------------+-----------------+
| Variable_name        | Value           |
+----------------------+-----------------+
| collation_connection | utf8_general_ci | 
| collation_database   | utf8_general_ci | 
| collation_server     | utf8_general_ci | 
+----------------------+-----------------+
3 rows in set (0.00 sec)
mysql>
mysql的字符集分的比較細，可以采用默認值，也可以指定值
 
A.數據庫字符集
使用默認字符集的庫
mysql> create database db1;
Query OK, 1 row affected (0.01 sec)
 
mysql> show create database db1;
+----------+--------------------------------------------------------------+
| Database | Create Database                                              |
+----------+--------------------------------------------------------------+
| db1      | CREATE DATABASE `db1` /*!40100 DEFAULT CHARACTER SET utf8 */ | 
+----------+--------------------------------------------------------------+
1 row in set (0.00 sec)
指定字符集的庫
mysql> create database db2 default character set latin1;
Query OK, 1 row affected (0.01 sec)
mysql> show create database db2;
+----------+----------------------------------------------------------------+
| Database | Create Database                                                |
+----------+----------------------------------------------------------------+
| db2      | CREATE DATABASE `db2` /*!40100 DEFAULT CHARACTER SET latin1 */ | 
+----------+----------------------------------------------------------------+
1 row in set (0.00 sec)
 
修改庫的字符集
mysql> alter database db2 default character set utf8;
Query OK, 1 row affected (0.00 sec)
mysql> show create database db2;
+----------+--------------------------------------------------------------+
| Database | Create Database      www.2cto.com                                            |
+----------+--------------------------------------------------------------+
| db2      | CREATE DATABASE `db2` /*!40100 DEFAULT CHARACTER SET utf8 */ | 
+----------+--------------------------------------------------------------+
1 row in set (0.00 sec)
 
B.表字符集
mysql> use db2;
Database changed
 
使用默認庫字符集的表
mysql> create table t1(a varchar(10));
Query OK, 0 rows affected (0.01 sec)
mysql> show create table t1;
+-------+-----------------------------------------------------------------------------------------+
| Table | Create Table                                                                            |
+-------+-----------------------------------------------------------------------------------------+
| t1    | CREATE TABLE `t1` (
  `a` varchar(10) default NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 | 
+-------+-----------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
 
創建指定字符集的表
mysql> create table t2(a varchar(10)) default character set latin1;;
Query OK, 0 rows affected (0.01 sec)
ERROR: 
No query specified
mysql> show create table t2;
+-------+-------------------------------------------------------------------------------------------+
| Table | Create Table                                                                              |
+-------+-------------------------------------------------------------------------------------------+
| t2    | CREATE TABLE `t2` (
  `a` varchar(10) default NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 | 
+-------+-------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
 
更改表的字符集
mysql> alter table t2 default character set utf8;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> show create table t2;
+-------+--------------------------------------------------------------------------------------------------------------+
| Table | Create Table     www.2cto.com                                                                                                |
+-------+--------------------------------------------------------------------------------------------------------------+
| t2    | CREATE TABLE `t2` (
  `a` varchar(10) character set latin1 default NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 | 
+-------+--------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql>
從上面可以看到，修改表的字符集時，不會影響已經存在列的字符集，但新增列將繼承表的字符集，如下
mysql> alter table t2 add a2 varchar(10);
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> show create table t2;
+-------+-----------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                  |
+-------+-----------------------------------------------------------------------------------------------------------------------------------------------+
| t2    | CREATE TABLE `t2` (
  `a` varchar(10) character set latin1 default NULL,
  `a2` varchar(10) default NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 | 
+-------+-----------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
mysql>
 
如果想更改已經存在表和字符列的字符集，要用如下
mysql> alter table t2 convert to character set latin1;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> show create table t2;
+-------+----------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                               |
+-------+----------------------------------------------------------------------------------------------------------------------------+
| t2    | CREATE TABLE `t2` (
  `a` varchar(10) default NULL,
  `a2` varchar(10) default NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 | 
+-------+----------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
 
C.字段字符集
 
使用默認和指定字符集創建的列
mysql> create table t3 (a1 varchar(10),a2 varchar(10) character set latin1);
Query OK, 0 rows affected (0.04 sec)  www.2cto.com  
mysql> show create table t3;
+-------+------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                   |
+-------+------------------------------------------------------------------------------------------------------------------------------------------------+
| t3    | CREATE TABLE `t3` (
  `a1` varchar(10) default NULL,
  `a2` varchar(10) character set latin1 default NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 | 
+-------+------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql>
 
查看列的字符集
mysql> show full columns from t3;
+-------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
| Field | Type        | Collation         | Null | Key | Default | Extra | Privileges                      | Comment |
+-------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
| a1    | varchar(10) | utf8_general_ci   | YES  |     | NULL    |       | select,insert,update,references |         | 
| a2    | varchar(10) | latin1_swedish_ci | YES  |     | NULL    |       | select,insert,update,references |         | 
+-------+-------------+-------------------+------+-----+---------+-------+---------------------------------+---------+
2 rows in set (0.01 sec)
 
修改列的字符集
mysql> alter table t3 change a2 a2 varchar(10) character set utf8;
Query OK, 0 rows affected (0.03 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> show full columns from t3;
+-------+-------------+-----------------+------+-----+---------+-------+---------------------------------+---------+
| Field | Type        | Collation       | Null | Key | Default | Extra | Privileges                      | Comment |
+-------+-------------+-----------------+------+-----+---------+-------+---------------------------------+---------+
| a1    | varchar(10) | utf8_general_ci | YES  |     | NULL    |       | select,insert,update,references |         | 
| a2    | varchar(10) | utf8_general_ci | YES  |     | NULL    |       | select,insert,update,references |         | 
+-------+-------------+-----------------+------+-----+---------+-------+---------------------------------+---------+
2 rows in set (0.00 sec)
mysql>
 
結論：字符集從數據庫、表、列的字符集是逐級繼承的關系
 
查看字符集命令
mysql> show create table t4; //顯示表字符集
mysql> show create database db2; //顯示庫字符集
mysql> show full columns from t4; //顯示列字符集
alter database db2 default character set utf8; //更改庫的字符集
alter table t2 convert to character set latin1;//更改表的現存列字符集
alter table t2 default character set utf8;  //更能改表的默認字符集
alter table t3 change a2 a2 varchar(10) character set utf8; //更能改字段的字符集
   www.2cto.com  
2.修改mysql的默認存儲引擎
mysql> show variables like 'storage%';
+----------------+--------+
| Variable_name  | Value  |
+----------------+--------+
| storage_engine | MyISAM | 
+----------------+--------+
1 row in set (0.01 sec)
mysql>
 
在[mysqld]下添加如下參數
default-storage-engine=innodb
 
重啟mysql服務，查看
mysql> show variables like 'storage%';
+----------------+--------+
| Variable_name  | Value  |
+----------------+--------+
| storage_engine | InnoDB | 
+----------------+--------+
1 row in set (0.01 sec)
mysql>
 
創建默認字符集的表
mysql> create table t4 (a1 int);
Query OK, 0 rows affected (0.01 sec)
mysql> show create table t4;
+-------+--------------------------------------------------------------------------------------+
| Table | Create Table                                                                         |
+-------+--------------------------------------------------------------------------------------+
| t4    | CREATE TABLE `t4` (
  `a1` int(11) default NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 | 
+-------+--------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
 
更改表的默認字符集
mysql> alter table t4 engine myisam;
Query OK, 0 rows affected (0.06 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> show create table t4;
+-------+--------------------------------------------------------------------------------------+  www.2cto.com  
| Table | Create Table                                                                         |
+-------+--------------------------------------------------------------------------------------+
| t4    | CREATE TABLE `t4` (
  `a1` int(11) default NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8 | 
+-------+--------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql>
 

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