【已解决】Windows下 MySQL大小写敏感解决方案及分析

Windows下 MySQL大小写敏感配置

zoerywzhou@163.com

作者：Zhouwan

2017-3-27

最近在window系统下操作Linux系统下创建的数据库，发现有些不对劲，比较了半天才发现是大小写敏感的问题造成的。网上搜索了一下，解决了这个问题，做个简明扼要的记录。

按照网上的说明：

WINDOWS：

编辑MySQL安装目录下的my.ini 文件，在[mysqld]节下添加 lower_case_table_names=0 (备注：为0时大小写敏感，为1时大小写不敏感，默认为1)，可以实现MySql按照建表Sql语句的大小写状态来定义表名。

具体操作的时候会发现，理论和实践总是有差异的：

我的MySQL安装路径为：C:\Program Files\MySQL\MySQL Server 5.7\bin（网上有的说my.ini配置文件在这个文件夹下）

但是my.ini所在的文件路径为：C:\ProgramData\MySQL\MySQL Server 5.7\my.ini

然后在[mysqld]节下添加 lower_case_table_names=0。

配置好文件了，去试一下咋样。

然后，还没重启系统进行测试，在另一个博文里看到了官方手册的网址链接，按捺不住好奇心去看一下。发现上面的这个配置是不可行的（具体分析见下面的划重点）

MySQL官网手册-大小写敏感说明:

（在官网说明的基础上加上我的独家中文解说 O(∩_∩)O~英文好的同学最好直接看英文文档，说的比较清楚）

How table and database names are stored on disk and used in MySQL is affected by the lower_case_table_names system variable, which you can set when starting mysqld. lower_case_table_names can take the values shown in the following table. This variable does not affect case sensitivity of trigger identifiers. On. On . On .

Value Meaning

Value	Meaning
`0`	Table and database names are stored on disk using the lettercase specified in the `CREATE TABLE` or `CREATE DATABASE` statement. Name comparisons are case sensitive. （总结：存储和查询的时候都大小写敏感，都要是按照建表时指定的写法） You should not set this variable to 0 if you are running MySQL on a system that has case-insensitive file names (such as Windows or OS X). If you force this variable to 0 with `--lower-case-table-names=0` on a case-insensitive file system and access `MyISAM` tablenames using different lettercases, index corruption may result.（此处划重点）
`1`	Table names are stored in lowercase on disk and name comparisons are not case sensitive. MySQL converts all table names to lowercase on storage and lookup. This behavior also applies to database names and table aliases. （总结：存储和查询的时候大小写都不敏感，都转换为小写字母）
`2`	Table and database names are stored on disk using the lettercase specified in the `CREATE TABLE` or `CREATE DATABASE` statement, but MySQL converts them to lowercase on lookup. Name comparisons are not case sensitive. This works only on file systems that are not case sensitive! `InnoDB` table names are stored in lowercase, as for `lower_case_table_names=1`. （总结：存储时大小写敏感，按照建表时指定的写法；查询时都转换为小写字母）

0

Table and database names are stored on disk using the lettercase specified in the CREATE TABLE or CREATE DATABASE statement. Name comparisons are case sensitive.

（总结：存储和查询的时候都大小写敏感，都要是按照建表时指定的写法）

You should not set this variable to 0 if you are running MySQL on a system that has case-insensitive file names (such as Windows or OS X). If you force this variable to 0 with --lower-case-table-names=0 on a case-insensitive file system and access MyISAM tablenames using different lettercases, index corruption may result.（此处划重点）

1

Table names are stored in lowercase on disk and name comparisons are not case sensitive. MySQL converts all table names to lowercase on storage and lookup. This behavior also applies to database names and table aliases.

（总结：存储和查询的时候大小写都不敏感，都转换为小写字母）

2

Table and database names are stored on disk using the lettercase specified in the CREATE TABLE or CREATE DATABASE statement, but MySQL converts them to lowercase on lookup. Name comparisons are not case sensitive. This works only on file systems that are not case sensitive! InnoDB table names are stored in lowercase, as for lower_case_table_names=1.

（总结：存储时大小写敏感，按照建表时指定的写法；查询时都转换为小写字母）

1、单平台：If you are using MySQL on only one platform, you do not normally have to change the lower_case_table_names variable from its default value.

2、跨平台：However, you may encounter difficulties if you want to transfer tables between platforms that differ in file system case sensitivity. For example, on Unix, you can have two different tables named my_table and MY_TABLE, but on Windows these two names are considered identical. To avoid data transfer problems arising from lettercase of database or table names, you have two options:（跨平台的MySQL大小写敏感解决方案在此！！！看看官网怎么说~）

Use lower_case_table_names=1 on all systems. The main disadvantage with this is that when you use SHOW TABLES or SHOW DATABASES, you do not see the names in their original lettercase.
Use lower_case_table_names= on Windows. This preserves the lettercase of database and table names. The disadvantage of this is that you must ensure that your statements always refer to your database and table names with the correct lettercase on Windows. If you transfer your statements to Unix, where lettercase is significant, they do not work if the lettercase is incorrect.

Exception: If you are using InnoDB tables and you are trying to avoid these data transfer problems, you should set lower_case_table_names to 1 on all platforms to force names to be converted to lowercase.

有点复杂。。。本来看懂了的，又出来了个Exception。。。本来愉悦的心情又down了，因为我的table就是InnoDB，看了半天想去配置文件大展身手来着。。。

好吧，那就先不管跨不跨平台了，也不管配置文件my.ini了。直接上手使用的话，想要区别大小写，可以在查询语句的时候加上Binary，具体实现如下：

三个方案：

1、在建表时指定大小写敏感：

　　MySql默认查询是不区分大小写的,如果需要区分他,必须在建表的时候,Binary标示敏感的属性.

　　CREATE TABLE NAME(
　　name VARCHAR(10) BINARY);

2、在查询条件的字段名前加上binary：

　　在SQL语句中实现 SELECT * FROM TABLE NAME WHERE BINARY name='Clip';

3、设置字符集使其大小写敏感：

　　utf8_general_ci --不区分大小写

　　utf8_bin--区分大小写

【设置collate（校对）。 collate规则：

　　*_bin: 表示的是binary case sensitive collation，也就是说是区分大小写的
　　*_cs: case sensitive collation，区分大小写
　　*_ci: case insensitive collation，不区分大小写】

4、可以修改该字段的collation 为 binary
比如：
ALTER TABLE TABLENAME MODIFY COLUMN COLUMNNAME VARCHAR(50) BINARY CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL;

（此段文字的参考博文：http://www.cnblogs.com/softidea/p/6047766.html）