# 测试utf8的大小写敏感性及其修改方法

-- 以下是utf8不区分大小写
1 # 修改数据库:  
2 ALTER DATABASE database_name CHARACTER SET = utf8 COLLATE = utf8_general_ci;  
3 # 修改表:  
4 ALTER TABLE table_name CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;  
5 # 修改表字段:  
6 ALTER TABLE table_name CHANGE column_name column_name VARCHAR(191) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL;  

-- 以下是utf8区分大小写
1 # 修改数据库:  
2 ALTER DATABASE database_name CHARACTER SET = utf8 COLLATE = utf8_bin;  
3 # 修改表:  
4 ALTER TABLE table_name CONVERT TO CHARACTER SET utf8 COLLATE utf8_bin;  
5 # 修改表字段:  
6 ALTER TABLE table_name CHANGE column_name column_name VARCHAR(191) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL;  

-- 1、删除库
drop database if exists db2019;
mysql> drop database if exists db2019;
Query OK, 0 rows affected, 1 warning (0.00 sec)

-- 2、创建字符集为utf8的库
create database db2019 DEFAULT CHARACTER SET utf8;
mysql> create database db2019 DEFAULT CHARACTER SET utf8;
Query OK, 1 row affected (0.00 sec)

-- 3、查看建库语句
show create database db2019;
mysql> show create database db2019;
+----------+-----------------------------------------------------------------+
| Database | Create Database                                                 |
+----------+-----------------------------------------------------------------+
| db2019   | CREATE DATABASE `db2019` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+-----------------------------------------------------------------+
1 row in set (0.00 sec)

-- 4、创建测试表和数据
use db2019;
-- drop table if exists tbl_test ;
create table tbl_test (
  id bigint(20) NOT NULL AUTO_INCREMENT,
  name varchar(20) NOT NULL,
  PRIMARY KEY (id),
  KEY idx_name (name)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ;

-- 5、查看创建表的语句
-- use db2019;
show create table tbl_test\G;
mysql> show create table tbl_test\G;
*************************** 1. row ***************************
       Table: tbl_test
Create Table: CREATE TABLE `tbl_test` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `idx_name` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

ERROR: 
No query specified

-- 6、查看默认字符集
-- 方法1、show variables like ‘%character%‘;
mysql> show variables like ‘%character%‘;
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | utf8                    |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | utf8                       |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)
-- 方法2、show variables like ‘collation%‘;
mysql> show variables like ‘collation%‘;
+----------------------+--------------------+
| Variable_name        | Value              |
+----------------------+--------------------+
| collation_connection | utf8_general_ci    |
| collation_database   | utf8_general_ci |
| collation_server     | utf8_general_ci    |
+----------------------+--------------------+
3 rows in set (0.00 sec)

-- 8、查看默认校对规则
show collation like ‘utf8%‘;
mysql>  show collation like ‘utf8%‘;
+--------------------------+---------+-----+---------+----------+---------+
| Collation                | Charset | Id  | Default | Compiled | Sortlen |
+--------------------------+---------+-----+---------+----------+---------+
| utf8_general_ci          | utf8    |  33 | Yes     | Yes      |       1 |
| utf8_bin                 | utf8    |  83 |         | Yes      |       1 |
| utf8_bin          | utf8    | 192 |         | Yes      |       8 |
| utf8_icelandic_ci        | utf8    | 193 |         | Yes      |       8 |
| utf8_latvian_ci          | utf8    | 194 |         | Yes      |       8 |
| utf8_romanian_ci         | utf8    | 195 |         | Yes      |       8 |
| utf8_slovenian_ci        | utf8    | 196 |         | Yes      |       8 |
| utf8_polish_ci           | utf8    | 197 |         | Yes      |       8 |
| utf8_estonian_ci         | utf8    | 198 |         | Yes      |       8 |
| utf8_spanish_ci          | utf8    | 199 |         | Yes      |       8 |
| utf8_swedish_ci          | utf8    | 200 |         | Yes      |       8 |
| utf8_turkish_ci          | utf8    | 201 |         | Yes      |       8 |
| utf8_czech_ci            | utf8    | 202 |         | Yes      |       8 |
| utf8_danish_ci           | utf8    | 203 |         | Yes      |       8 |
| utf8_lithuanian_ci       | utf8    | 204 |         | Yes      |       8 |
| utf8_slovak_ci           | utf8    | 205 |         | Yes      |       8 |
| utf8_spanish2_ci         | utf8    | 206 |         | Yes      |       8 |
| utf8_roman_ci            | utf8    | 207 |         | Yes      |       8 |
| utf8_persian_ci          | utf8    | 208 |         | Yes      |       8 |
| utf8_esperanto_ci        | utf8    | 209 |         | Yes      |       8 |
| utf8_hungarian_ci        | utf8    | 210 |         | Yes      |       8 |
| utf8_sinhala_ci          | utf8    | 211 |         | Yes      |       8 |
| utf8_german2_ci          | utf8    | 212 |         | Yes      |       8 |
| utf8_croatian_ci         | utf8    | 213 |         | Yes      |       8 |
| utf8_unicode_520_ci      | utf8    | 214 |         | Yes      |       8 |
| utf8_vietnamese_ci       | utf8    | 215 |         | Yes      |       8 |
| utf8_general_mysql500_ci | utf8    | 223 |         | Yes      |       1 |
| utf8_general_ci       | utf8 |  45 | Yes     | Yes      |       1 |
| utf8_bin              | utf8 |  46 |         | Yes      |       1 |
| utf8_bin       | utf8 | 224 |         | Yes      |       8 |
| utf8_icelandic_ci     | utf8 | 225 |         | Yes      |       8 |
| utf8_latvian_ci       | utf8 | 226 |         | Yes      |       8 |
| utf8_romanian_ci      | utf8 | 227 |         | Yes      |       8 |
| utf8_slovenian_ci     | utf8 | 228 |         | Yes      |       8 |
| utf8_polish_ci        | utf8 | 229 |         | Yes      |       8 |
| utf8_estonian_ci      | utf8 | 230 |         | Yes      |       8 |
| utf8_spanish_ci       | utf8 | 231 |         | Yes      |       8 |
| utf8_swedish_ci       | utf8 | 232 |         | Yes      |       8 |
| utf8_turkish_ci       | utf8 | 233 |         | Yes      |       8 |
| utf8_czech_ci         | utf8 | 234 |         | Yes      |       8 |
| utf8_danish_ci        | utf8 | 235 |         | Yes      |       8 |
| utf8_lithuanian_ci    | utf8 | 236 |         | Yes      |       8 |
| utf8_slovak_ci        | utf8 | 237 |         | Yes      |       8 |
| utf8_spanish2_ci      | utf8 | 238 |         | Yes      |       8 |
| utf8_roman_ci         | utf8 | 239 |         | Yes      |       8 |
| utf8_persian_ci       | utf8 | 240 |         | Yes      |       8 |
| utf8_esperanto_ci     | utf8 | 241 |         | Yes      |       8 |
| utf8_hungarian_ci     | utf8 | 242 |         | Yes      |       8 |
| utf8_sinhala_ci       | utf8 | 243 |         | Yes      |       8 |
| utf8_german2_ci       | utf8 | 244 |         | Yes      |       8 |
| utf8_croatian_ci      | utf8 | 245 |         | Yes      |       8 |
| utf8_unicode_520_ci   | utf8 | 246 |         | Yes      |       8 |
| utf8_vietnamese_ci    | utf8 | 247 |         | Yes      |       8 |
+--------------------------+---------+-----+---------+----------+---------+
53 rows in set (0.00 sec)

mysql> 

-- 9、插入测试数据
-- use db2019;
insert into tbl_test(name) values(‘aaa‘);
insert into tbl_test(name) values(‘bbb‘);
insert into tbl_test(name) values(‘AAA‘);
insert into tbl_test(name) values(‘BBB‘);

mysql> select * from tbl_test;
+----+------+
| id | name |
+----+------+
|  1 | aaa  |
|  3 | AAA  |
|  2 | bbb  |
|  4 | BBB  |
+----+------+
4 rows in set (0.00 sec)

mysql> select * from tbl_test where name=‘aaa‘;
+----+------+
| id | name |
+----+------+
|  1 | aaa  |
|  3 | AAA  |
+----+------+
2 rows in set (0.00 sec)

-- 10、默认情况下,不区分大小写,修改成大小写敏感
-- alter database db2019 character set=utf8;
alter database db2019 character set=utf8 collate=utf8_bin;

-- alter table tbl_test convert to character set utf8 ;
alter table tbl_test convert to character set utf8 collate utf8_bin;

-- 只修改这个即可实现区分大小写
-- alter table tbl_test change name name varchar(20)  character set utf8 collate utf8_general_ci not null;
-- alter table tbl_test modify name varchar(20)  character set utf8 collate utf8_general_ci not null;
alter table tbl_test change name name varchar(20)  character set utf8 collate utf8_bin not null;
alter table tbl_test modify name varchar(20)  character set utf8 collate utf8_bin not null;

mysql> alter database db2019 character set=utf8 collate=utf8_bin;
Query OK, 1 row affected (0.00 sec)

mysql> show create database db2019;
+----------+----------------------------------------------------------------------------------+
| Database | Create Database                                                                  |
+----------+----------------------------------------------------------------------------------+
| db2019   | CREATE DATABASE `db2019` /*!40100 DEFAULT CHARACTER SET utf8 COLLATE utf8_bin */ |
+----------+----------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> select * from tbl_test where name=‘aaa‘;
+----+------+
| id | name |
+----+------+
|  1 | aaa  |
|  3 | AAA  |
+----+------+
2 rows in set (0.00 sec)
-- 此时只修改库级别的还不行，仍然还需要修改表级别的
mysql> alter table tbl_test convert to character set utf8 collate utf8_bin;
Query OK, 4 rows affected (0.08 sec)
Records: 4  Duplicates: 0  Warnings: 0
mysql> select * from tbl_test where name=‘aaa‘;
+----+------+
| id | name |
+----+------+
|  1 | aaa  |
+----+------+
1 row in set (0.00 sec)