--- 简单记录未做代码验证 公众号 MySQL学习 ---  hex(col) 返回字符集直接从database charset拿，跳过了转换，直接返回二进制，可以用于测试数据库存储的是什么字符集。（需要后期代码验证） hex('去') 在client charset和connect charset设置一致的情况下，不需要转换，hex直接返回输入字符的二进制，可以用于测试终端到底是字符集。（需要后期代码验证） set names 设置 client charset/connect charset/result charset 诊断乱码， 1、可以先查询client charset/connect charset/result charset是否一致，不一致先设置为一致。 2、然后查看数据库存储的字符集是什么 3、然后查看client charset/connect charset/result charset是否和它一致，然后查看终端字符集是否一致。 终端UTF8 mysql> select hex(name),name,hex('去') from testchr; +-----------+------+-----------+ | hex(name) | name | hex('?') | +-----------+------+-----------+ | E58EBB | ? | C8A5 | | C8A5 | ? | C8A5 | | C8A5 | ? | C8A5 | +-----------+------+-----------+ mysql> show variables like '%char%'; +---------------------------+--------------------------------------------+ | Variable_name | Value | +---------------------------+--------------------------------------------+ | character_set_client | utf8 | | character_set_connection | gbk | | character_set_database | utf8 | | character_set_filesystem | binary | | character_set_results | gbk | | character_set_server | utf8 | | character_set_system | utf8 | | character_sets_dir | /newdata/mysql3306/install/share/charsets/ | | ft_query_extra_word_chars | OFF | +---------------------------+--------------------------------------------+ 9 rows in set (0.01 sec) mysql> 1、终端 GBK->names GBK->存储utf8 转换正常 2、终端 GBK->names utf8->存储utf8 把GBK当做UTF8存储，UTF8有2字节字符。 GBK存入utf8 mysql> select hex(name) from testchr; +-----------+ | hex(name) | +-----------+ | E58EBB | | C8A5 | +-----------+ 2 rows in set (0.00 sec) 3、终端UTF8->names gbk->存储utf8 终端转入names gbk 失败 mysql> insert into testchr values('去'); ERROR 1406 (22001): Data too long for column 'name' at row 1 4、终端UTF8->names gbk->存储GBK，因为GBK没有1字节的，也就是将UTF8当做GBK想存入数据库的GBK中。 转换失败 mysql> insert into testchr2 values('去'); ERROR 1366 (HY000): Incorrect string value: '\xBB' for column 'name' at row 1 5、终端GBK->names utf8->储存gbk，因为C8A5不是有效的UTF8字符，也就是想把GBK当做UTF8做转换存入GBK。 转换失败 mysql> insert into testchr2 values('去'); ERROR 1366 (HY000): Incorrect string value: '\xC8\xA5' for column 'name' at row 1 做好几种字符集一致即可。 6、终端utf8，更改character_set_connection测试 mysql> show variables like '%char%'; +---------------------------+--------------------------------------------+ | 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 | /newdata/mysql3306/install/share/charsets/ | | ft_query_extra_word_chars | OFF | +---------------------------+--------------------------------------------+ 9 rows in set (0.01 sec) mysql> set character_set_connection=gbk; Query OK, 0 rows affected (0.00 sec) mysql> select ('去'); +-----+ | 去 | +-----+ | 去 | +-----+ 1 row in set (0.00 sec) mysql> select hex('去'); +------------+ | hex('去') | +------------+ | C8A5 | +------------+ 1 row in set (0.00 sec) mysql> set character_set_connection=utf8; Query OK, 0 rows affected (0.00 sec) mysql> select hex('去'); +------------+ | hex('去') | +------------+ | E58EBB | +------------+ 1 row in set (0.00 sec)