MySQL字符集乱码

悠悠 2022-01-21 03:35 298阅读 0赞

MySQL数据库查询结果乱码，这是大家比较常见的情形。到底是什么原因导致出现查询结果为乱码呢，本文主要通过演示来理解乱码产生的原因，以及如何解决字符集乱码，供大家参考。

一、字符编码对比

SELECT hex(convert('love' USING latin1)) latin_value,
    	       hex(convert('love' USING gb2312)) gb2312_value,
    	       hex(convert('love' USING gbk))    gbk_value,
    	       hex(convert('love' USING utf8))   utf8_value;
    	+-------------+--------------+-----------+------------+
    	| latin_value | gb2312_value | gbk_value | utf8_value |
    	+-------------+--------------+-----------+------------+
    	| 6C6F7665    | 6C6F7665     | 6C6F7665  | 6C6F7665   |
    	+-------------+--------------+-----------+------------+
    	
    	SELECT hex(convert('爱' USING latin1)) latin_value,
    	       hex(convert('爱' USING gb2312)) gb2312_value,
    	       hex(convert('爱' USING gbk))    gbk_value,
    	       hex(convert('爱' USING utf8))   utf8_value;
    	+-------------+--------------+-----------+------------+
    	| latin_value | gb2312_value | gbk_value | utf8_value |
    	+-------------+--------------+-----------+------------+
    	| 3F          | B0AE         | B0AE      | E788B1     |
    	+-------------+--------------+-----------+------------+  
    	
    	SELECT convert(0x3F USING latin1)   latin_value,
    	       convert(0xB0AE USING gb2312) gb2312_value,
    	       convert(0xB0AE USING gbk)    gbk_value,
    	       convert(0xE788B1 USING utf8) utf8_value;
       
    	+-------------+--------------+-----------+------------+
    	| latin_value | gb2312_value | gbk_value | utf8_value |
    	+-------------+--------------+-----------+------------+
    	| ?           | 爱           | 爱        | 爱         |
    	+-------------+--------------+-----------+------------+

二、乱码测试

1、环境准备

# grep -Ev "^#|^$" /etc/my.cnf   -- 查看当前my.cnf配置
    	
    	mysql> show variables like 'version';
    	+---------------+------------+
    	| Variable_name | Value      |
    	+---------------+------------+
    	| version       | 5.7.23-log |
    	+---------------+------------+
    
    	mysql> show variables like '%character%';
    	
    	+--------------------------+----------------------------+
    	| Variable_name            | Value                      |
    	+--------------------------+----------------------------+
    	| character_set_client     | gbk                        |
    	| character_set_connection | gbk                        |
    	| character_set_database   | latin1                     |
    	| character_set_filesystem | binary                     |
    	| character_set_results    | gbk                        |
    	| character_set_server     | latin1                     |
    	| character_set_system     | utf8                       |
    	| character_sets_dir       | /usr/share/mysql/charsets/ |
    	+--------------------------+----------------------------+
    
    	DROP TABLE IF EXISTS sakila.colum_charset;
    	
    	CREATE TABLE sakila.colum_charset
    	(
    	   id int not null auto_increment primary key,
    	   c1 varchar(20),
    	   c2 char(20) CHAR SET gbk,
    	   c3 varchar(20) CHARSET gb2312,
    	   c4 char(20) CHARACTER SET utf8,
    	   c5 varchar(20) CHARSET utf8mb4
    	);
    	
    	mysql> show create table sakila.colum_charset\G
    	*************************** 1. row ***************************
    	       Table: colum_charset
    	Create Table: CREATE TABLE `colum_charset` (
    	  `id` int(11) NOT NULL AUTO_INCREMENT,
    	  `c1` varchar(20) DEFAULT NULL,
    	  `c2` char(20) CHARACTER SET gbk DEFAULT NULL,
    	  `c3` varchar(20) CHARACTER SET gb2312 DEFAULT NULL,
    	  `c4` char(20) CHARACTER SET utf8 DEFAULT NULL,
    	  `c5` varchar(20) CHARACTER SET utf8mb4 DEFAULT NULL,
    	  PRIMARY KEY (`id`)
    	) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=latin1

2、基于默认字符插入数据(gbk)  
– character\_set\_client gbk  
– character\_set\_connection gbk  
– character\_set\_results gbk

INSERT INTO sakila.colum_charset(id,
    	                                 c1,
    	                                 c2,
    	                                 c3,
    	                                 c4,
    	                                 c5)
    	VALUES (NULL,'爱','爱','爱','爱','爱');
    	        
    	ERROR 1366 (HY000): Incorrect string value: '\xB0\xAE' for column 'c1' at row 1
    
    	INSERT INTO sakila.colum_charset(id,
    	                                 c1,
    	                                 c2,
    	                                 c3,
    	                                 c4,
    	                                 c5)
    	VALUES (NULL,'love','爱','爱','爱','爱');
    	Query OK, 1 row affected (0.00 sec)
    	
    	mysql> select * from sakila.colum_charset;
    	+----+------+------+------+------+------+
    	| id | c1   | c2   | c3   | c4   | c5   |
    	+----+------+------+------+------+------+
    	|  1 | love | 爱   | 爱   | 爱   | 爱   |
    	+----+------+------+------+------+------+

3、三个变量全部设置为utf8插入数据  
mysql> set names ‘utf8’;  
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like '%character%';
    	+--------------------------+----------------------------+
    	| Variable_name            | Value                      |
    	+--------------------------+----------------------------+
    	| character_set_client     | utf8                       |
    	| character_set_connection | utf8                       |
    	| character_set_database   | latin1                     |
    	| character_set_filesystem | binary                     |
    	| character_set_results    | utf8                       |
    	| character_set_server     | latin1                     |
    	| character_set_system     | utf8                       |
    	| character_sets_dir       | /usr/share/mysql/charsets/ |
    	+--------------------------+----------------------------+
    	
    	INSERT INTO sakila.colum_charset(id,
    	                                 c1,
    	                                 c2,
    	                                 c3,
    	                                 c4,
    	                                 c5)
    	VALUES (NULL,'heart','心','心','心','心');        
    	Query OK, 1 row affected (0.00 sec)
    	
    	mysql> select * from sakila.colum_charset;
    	+----+-------+------+------+------+------+
    	| id | c1    | c2   | c3   | c4   | c5   |
    	+----+-------+------+------+------+------+
    	|  1 | love  | 爱   | 爱   | 爱   | 爱   |
    	|  2 | heart | 心   | 心   | 心   | 心   |
    	+----+-------+------+------+------+------+
    
    	INSERT INTO sakila.colum_charset(id,
    	                                 c1,
    	                                 c2,
    	                                 c3,
    	                                 c4,
    	                                 c5)
    	VALUES (NULL,'heart','屌','屌','屌','屌');  -- c3列为gb2312编码
    	        
    	ERROR 1366 (HY000): Incorrect string value: '\xE5\xB1\x8C' for column 'c3' at row 1

4、单个变量character\_set\_connection设置为latin1插入数据  
mysql> set character\_set\_connection=latin1;

INSERT INTO sakila.colum_charset(id,
    	                                 c1,
    	                                 c2,
    	                                 c3,
    	                                 c4,
    	                                 c5)
    	VALUES (NULL,'heart','情','情','情','情');
    	Query OK, 1 row affected, 4 warnings (0.00 sec)
    	
    	mysql> show warnings \G
    	*************************** 1. row ***************************
    	  Level: Warning
    	   Code: 1300
    	Message: Invalid utf8 character string: '\xE6\x83\x85'
    	
    	-- 乱码出现
    	mysql> select * from sakila.colum_charset;
    	+----+-------+------+------+------+------+
    	| id | c1    | c2   | c3   | c4   | c5   |
    	+----+-------+------+------+------+------+
    	|  1 | love  | 爱   | 爱   | 爱   | 爱   |
    	|  2 | heart | 心   | 心   | 心   | 心   |
    	|  3 | heart | ?    | ?    | ?    | ?    |
    	+----+-------+------+------+------+------+

5、单个变量character\_set\_connection设置为gb2312插入数据  
mysql> set character\_set\_connection=gb2312;

INSERT INTO sakila.colum_charset(id,
    	                                 c1,
    	                                 c2,
    	                                 c3,
    	                                 c4,
    	                                 c5)
    	VALUES (NULL,'heart','屌','屌','屌','屌');
    	
    	Query OK, 1 row affected, 4 warnings (0.00 sec)
        
    	mysql> select * from sakila.colum_charset;
    	+----+-------+------+------+------+------+
    	| id | c1    | c2   | c3   | c4   | c5   |
    	+----+-------+------+------+------+------+
    	|  1 | love  | 爱   | 爱   | 爱   | 爱   |
    	|  2 | heart | 心   | 心   | 心   | 心   |
    	|  3 | heart | ?    | ?    | ?    | ?    |
    	|  4 | heart | ?    | ?    | ?    | ?    |
    	+----+-------+------+------+------+------+

6、单个变量character\_set\_results设置为latin1  
– 测试返回数据

mysql> set character_set_results=latin1;
    	Query OK, 0 rows affected (0.00 sec)
    	
    	mysql> select * from sakila.colum_charset;
    	+----+-------+------+------+------+------+
    	| id | c1    | c2   | c3   | c4   | c5   |
    	+----+-------+------+------+------+------+
    	|  1 | love  | ?    | ?    | ?    | ?    |
    	|  2 | heart | ?    | ?    | ?    | ?    |
    	|  3 | heart | ?    | ?    | ?    | ?    |
    	|  4 | heart | ?    | ?    | ?    | ?    |
    	+----+-------+------+------+------+------+
    	4 rows in set (0.00 sec)

6、单个变量character\_set\_results设置为gb2312  
– 测试返回数据

mysql> set character_set_results=gb2312;
    	Query OK, 0 rows affected (0.00 sec)
    	
    	mysql> select * from sakila.colum_charset;
    	+----+-------+------+------+------+------+
    	| id | c1    | c2   | c3   | c4   | c5   |
    	+----+-------+------+------+------+------+
    	|  1 | love  |    |    |    |    |
    	|  2 | heart |    |    |    |    |
    	|  3 | heart | ?    | ?    | ?    | ?    |
    	|  4 | heart | ?    | ?    | ?    | ?    |
    	+----+-------+------+------+------+------+
    	4 rows in set (0.00 sec)

6、单个变量character\_set\_results设置为gbk  
– 测试返回数据  
mysql> set character\_set\_results=gbk;  
Query OK, 0 rows affected (0.00 sec)

mysql> select * from sakila.colum_charset;
    	+----+-------+------+------+------+------+
    	| id | c1    | c2   | c3   | c4   | c5   |
    	+----+-------+------+------+------+------+
    	|  1 | love  |    |    |    |    |
    	|  2 | heart |    |    |    |    |
    	|  3 | heart | ?    | ?    | ?    | ?    |
    	|  4 | heart | ?    | ?    | ?    | ?    |
    	+----+-------+------+------+------+------+
    	4 rows in set (0.00 sec)

7、单个变量character\_set\_results设置为utf8  
– 测试返回数据

mysql> set character_set_results=utf8;
    	Query OK, 0 rows affected (0.00 sec)
    	
    	mysql> select * from sakila.colum_charset;
    	+----+-------+------+------+------+------+
    	| id | c1    | c2   | c3   | c4   | c5   |
    	+----+-------+------+------+------+------+
    	|  1 | love  | 爱   | 爱   | 爱   | 爱   |
    	|  2 | heart | 心   | 心   | 心   | 心   |
    	|  3 | heart | ?    | ?    | ?    | ?    |
    	|  4 | heart | ?    | ?    | ?    | ?    |
    	+----+-------+------+------+------+------+
    	4 rows in set (0.00 sec)

8、本地环境变量影响客户端字符集设定  
– 在my.cnf中未配置客户端字符集，如果配置后，则使用配置文件中设定的字符集

==========================================================  
结论：  
character\_set\_client: 客户端发送的数据是什么编码？  
character\_set\_connection: 告诉字符集转换器，转换成什么编码？  
character\_set\_results: 查询的结果用什么编码？  
如果以上三者都为字符集N,可简写为set names ‘N’;

乱码产生的原因如下：  
a、插入或读取时对应编码环节发生转换导致数据丢失。  
b、如果两个字符集之间无法进行无损编码转换，一定会出现乱码。

解决方案：  
1、一定要保证character\_set\_connection字符集大于等于client字符集，否则会丢失数据  
比如： latin1 < gb2312 < gbk < utf8，  
若设置set character\_set\_client = gb2312，  
那么至少connection的字符集要大于等于gb2312，否则就会丢失数据  
2、一定要保证character\_set\_results大于等于数据存入的字符集，否则会丢失数据  
比如：如存储的字符为utf8,而返回character\_set\_results为gbk，数据被截断

3、所有变量使用统一的字符编码，如utf8或者utf8mb4