MySQL 字符类型大小写敏感

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

(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

(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

(root@localhost)[hello]> show create table test1G*************************** 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

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

(root@localhost)[hello]> show create table test1G*************************** 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

(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

(root@localhost)[hello]> create table test2(id int, name varchar(10) binary);(root@localhost)[hello]> show create table test2G*************************** 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

创建

create database <db_name> default character set utf8mb4 collate utf8mb4_bin;

修改

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

create table <tb_name> (......) engine=innodb default charset=utf8mb4 collate=utf8mb4_bin;

修改

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

create table <tb_name> (`field1` varchar(10) character set utf8mb4 collate utf8mb4_bin,......)

修改

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好吧啦网其它相关文章！