在mysql中存在着各种utf8编码格式,如下表:
1)utf8_bin
utf8_bin将字符串中的每一个字符用二进制数据存储,区分大小写。
2)utf8_general_ci
utf8_genera_ci不区分大小写,ci为case insensitive的缩写,即大小写不敏感。
3)utf8_general_cs
utf8_general_cs区分大小写,cs为case sensitive的缩写,即大小写敏感。
执行如下命令:
create table test_bin (
name varchar(32) not null primary key,
age int unsigned not null
) engine = InnoDB COLLATE=utf8_bin;
create table test_ci (
name varchar(32) not null primary key,
age int unsigned not null
) engine = InnoDB COLLATE=utf8_general_ci;
create table test_cs (
name varchar(32) not null primary key,
age int unsigned not null
) engine = InnoDB COLLATE=utf8_general_cs;
1,2命令成功 3执行失败,不支持utf8_genral_cs。
insert into test_bin values('Alice', 18);
insert into test_bin values('alice', 20);
以上命令能够执行成功,因为utf8_bin是以十六进制方式存储数据,两条记录的主键不重复。
insert into test_ci values('Alice', 18);
insert into test_ci values('alilce', 20);
以上命令执行失败,因为utf8_general_ci不区分大小写,两条记录的主键重复。
最后 看下官方的文档
case (in)sensitivity
https://dev.mysql.com/doc/refman/5.0/en/case-sensitivity.html
problems
https://bugs.mysql.com/bug.php?id=65830
https://bugs.mysql.com/bug.php?id=50909
https://bugs.mysql.com/bug.php?id=63164
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