mysql字符类型默认是不区分大小写的，即select * from t where name='AAA'与='aaa'没区别，以下是测试的例子
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(root@localhost)[hello]> create table test1(id int, name varchar(10));
(root@localhost)[hello]> insert into test1 values(1,'aaa'),(2,'AAA'),(3,'bbb'),(4,'BbB');
(root@localhost)[hello]> select * from test1;
+------+------+
| id | name |
+------+------+
| 1 | aaa |
| 2 | AAA |
| 3 | bbb |
| 4 | BbB |
+------+------+
(root@localhost)[hello]> select * from test1 where name = 'AAA';
+------+------+
| id | name |
+------+------+
| 1 | aaa |
| 2 | AAA |
+------+------+
(root@localhost)[hello]> select * from test1 where name = 'aaa';
+------+------+
| id | name |
+------+------+
| 1 | aaa |
| 2 | AAA |
+------+------+
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可以看到此时where条件后面的'AAA'与'aaa'，查出来的结果没啥区别。
如果只想找出'AAA'的可以有以下几种办法
1.在sql中加入binary关键字
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(root@localhost)[hello]> select * from test1 where binary name = 'AAA';
+------+------+
| id | name |
+------+------+
| 2 | AAA |
+------+------+
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2.修改列的定义
先查看原始表的定义
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(root@localhost)[hello]> show create table test1\G
*************************** 1. row ***************************
Table: test1
Create Table: CREATE TABLE `test1` (
`id` int(11) DEFAULT NULL,
`name` varchar(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
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修改表test1的name列
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alter table test1 modify column name varchar(10) character set utf8mb4 collate utf8mb4_bin default null;
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collate utf8mb4_bin表示where过滤或者order by排序区分大小写
此时查看test1的定义
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(root@localhost)[hello]> show create table test1\G
*************************** 1. row ***************************
Table: test1
Create Table: CREATE TABLE `test1` (
`id` int(11) DEFAULT NULL,
`name` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
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接着再执行查询语句
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(root@localhost)[hello]> select * from test1 where name='AAA';
+------+------+
| id | name |
+------+------+
| 2 | AAA |
+------+------+
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下面再创建一张test2表，就会发现上面修改列的语句其实相当于在创建表时varchar后面跟binary
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(root@localhost)[hello]> create table test2(id int, name varchar(10) binary);
(root@localhost)[hello]> show create table test2\G
*************************** 1. row ***************************
Table: test2
Create Table: CREATE TABLE `test2` (
`id` int(11) DEFAULT NULL,
`name` varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
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下面介绍如何设置字符大小写敏感
- 数据库级别设置字符大小写敏感
创建
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create database <db_name> default character set utf8mb4 collate utf8mb4_bin;
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修改
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alter database <db_name> default character set utf8mb4 collate utf8mb4_bin;
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- 表级别设置字符大小写敏感
创建
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create table <tb_name> (
......
) engine=innodb default charset=utf8mb4 collate=utf8mb4_bin;
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修改
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alter table <tb_name> engine=innodb default charset=utf8mb4 collate=utf8mb4_bin;
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- 列级别设置字符大小写敏感
创建
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create table <tb_name> (
`field1` varchar(10) character set utf8mb4 collate utf8mb4_bin,
......
)
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修改
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alter table <tb_name> modify column `field1` varchar(10) character set utf8mb4 collate utf8mb4_bin default null;
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继承关系是列-->表-->库，优先级是列>表>库
以上就是MySQL 字符类型大小写敏感的详细内容，更多关于MySQL 字符类型大小写的资料请关注服务器之家其它相关文章！
原文链接：https://www.cnblogs.com/ddzj01/p/10736670.html