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 |+------+------+ |
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 |+------+------+ |
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: test1Create Table: CREATE TABLE `test1` ( `id` int(11) DEFAULT NULL, `name` varchar(10) DEFAULT NULL) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 |
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; |
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: test1Create 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 |
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 |+------+------+ |
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: test2Create 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 |
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; |
修改
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alter database <db_name> default character set utf8mb4 collate utf8mb4_bin; |
- 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; |
修改
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alter table <tb_name> engine=innodb default charset=utf8mb4 collate=utf8mb4_bin; |
- 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,......) |
修改
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alter table <tb_name> modify column `field1` varchar(10) character set utf8mb4 collate utf8mb4_bin default null; |
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
