3、mysql faq
mysql
mysq.proc表 函数 存储过程
mysq.event表 event
触发器、视图：存放在库里面。（会生成对应的文件）
infomation_schema：虚拟内存 存放在内存里；
mysql backup： 用户数据库 mysql数据库；
数据库是所有it设施里性能最差的，性能短板。
nginx：并发量轻松上w 数据库，达到1k多，2k多，就慢的不行了。上w更笨达不到。 mysql：
mysql优化： 让mysql只干一件事儿：存数据。
笛卡尔乘积
即笛卡尔乘积，"雨露均沾"，利用 cross join实现
组合。（交叉连接是一种非常可怕的链接）
[root@iZbp1in7y9nitzcajdv0ufZ data]# touch {a,b}.{log,txt,html}
[root@iZbp1in7y9nitzcajdv0ufZ data]# ls
a.html a.log a.txt b.html b.log b.txt
数据库里，1w条记录，算小表。
千万级--才算是有一定规模的表；（百万级--中级）
2张小表（1w & 2w 交叉连接），交叉连接后，就变成亿级别了……这个就可怕了。
通常，mysql里是不会出现上亿级的，其性能会顶不住的。
oracle数据库---管理上亿级，轻松拿捏。
mysql里面不建议放上亿级。
但是真的达到了上亿级后，该怎么办呢？拆表！---分布式。
这个/var/lib/mysql目录就是存放mysql数据的地方
（很重要）
对应的目录就是mysql里的一个个数据库。
数据库：一些相关数据的集合（也就是磁盘上的目录）
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.002 sec)
MariaDB [(none)]>
这里的每一个目录就是一个数据库。（有3个实体数据库，真正存在磁盘上的）
information_schema不是一个磁盘目录数据库，它是一个内存数据库。
这个数据里有很多很多表，每个表其实对应了每个文件。
这里对应的都是一张张表。
user.frm这个表就是存放用户信息：
每个数据库都是由很多张表组成的。
进入数据库：
mysql.socket是数据库服务在启动过程中生成的
[root@linux-test ~]#ll /var/lib/mysql/mysql.sock
srwxrwxrwx 1 mysql mysql 0 Mar 31 10:02 /var/lib/mysql/mysql.sock
[root@linux-test ~]#mysqladmin -uroot -pxyy520 shutdown #手动停止mysql服务
[root@linux-test ~]#ll /var/lib/mysql/mysql.sock
ls: cannot access /var/lib/mysql/mysql.sock: No such file or directory
[root@linux-test ~]#ls /var/lib/mysql/
aria_log.00000001 ib_buffer_pool ib_logfile0 multi-master.info mysql_upgrade_info
aria_log_control ibdata1 ib_logfile1 mysql performance_schema
[root@linux-test ~]#
只要你mysql服务不启动，那么其mysql下的数据目录是不会生成数据的
mysql配置文件:/etc/my.cnf.d目录
范例：
当您在 my.cnf 文件中看到这行：
!includedir /etc/my.cnf.d
它的意思是 MySQL 服务器将包含（include）指定目录 /etc/my.cnf.d 下所有的 .cnf 配置文件。MySQL 会在启动时读取这些文件，并应用这些额外的配置设置。这种机制通常用于组织和分离不同的配置选项，例如，您可以有一个单独的文件用于配置复制相关的选项，另一个文件用于配置特定的表缓存大小等。
当使用 !includedir 指令时，MySQL 将按照字母顺序读取目录下的文件，因此，如果有多个文件设置了相同的配置项，最后读取的文件中的设置将会覆盖之前的设置。
这种设计允许软件包维护人员，系统管理员，或者用户自己添加和管理配置文件，而不必修改主配置文件 my.cnf。这样做的好处是可以避免在升级或其他维护操作中对主配置文件的改动。
「为什么 MySQL 采用 B+ 树作为索引？」的问答
来自：
小林coding
小林的回答：
B + 树的高度在 3 层时存储的数据可能已达千万级别，但对于跳表而言同样去维护千万的数据量那么所造成的跳表层数过高而导致的磁盘 io 次数增多，也就是使用 B + 树在存储 同样的数据下磁盘 io 次数更少。
「update 没加索引会锁全表？」的问答
来自：
小林coding
小林的回答：
网上很多人都说 update 不带索引就锁表，其实这是不对的。innodb 源码里面在扫码记录的时候，都是针对记录这个单位去加锁的， update 不带索引就是全表扫扫描，也就是表里的记录都加锁，所以大家误以为加了表锁，因此我的文章标题后面带了个问号
innodb 不会对 select、insert、delete、update 语句加表锁的，表锁在 inoodb 应用场景很少。
mysql命令操作历史
[root@linux-test ~]#cat ~/.mysql_history
mysql开发规范
现网数据库最佳配置实践😘
1、配置提示符
==范例：mysql的配置文件，修改提示符-2024.4.29(测试成功)==
[!NOTE]
本方法在
MariaDB 10.4.33、mysql5.6.47上均已成功测试。
- 查看mysql版本
[root@linux-test ~]#mysql -V
mysql Ver 15.1 Distrib 10.4.33-MariaDB, for Linux (x86_64) using readline 5.1
- 默认mysql提示符（不易于辨识当前登录的属于哪个用户、哪台主机、哪个数据库）
[root@linux-test ~]#mysql
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 20
Server version: 10.4.33-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]>
- 查看当前mysql默认提示符
[root@test1 ~]#mysql --print-defaults -v
mysql would have been started with the following arguments:
--default-character-set=utf8mb4 --prompt=\r:\m:\s(\u@\h) [\d]>\_
- man mysql帮助信息
##man mysql帮助信息
· Use an option file. You can set the prompt option in the [mysql] group of any MariaDB option file, such as /etc/my.cnf
or the .my.cnf file in your home directory. For example:
[mysql]
prompt=(\\u@\\h) [\\d]>\\_
- ==方法1：临时修改mysql提示符==
##临时修改mysql提示符
[root@linux-test ~]#mysql -uroot -pxyy520 --prompt="\\r:\\m:\\s(\\u@\\h) [\\d]>\\_"
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 21
Server version: 10.4.33-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
02:31:40(root@localhost) [(none)]>
##临时修改mysql提示符
[root@centos8 ~]#export MYSQL_PS1="\\r:\\m:\\s(\\u@\\h) [\\d]>\\_"
测试：
[root@linux-test ~]#export MYSQL_PS1="\\r:\\m:\\s(\\u@\\h) [\\d]>\\_"
[root@linux-test ~]#mysql
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 22
Server version: 10.4.33-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
08:27:55(root@localhost) [(none)]>
- ==方法2：持久修改mysql提示符（推荐）==
[root@centos8 ~]#vim /etc/my.cnf.d/mysql-clients.cnf
[mysql]
prompt="\\r:\\m:\\s(\\u@\\h) [\\d]>\\_"
- 测试（符合预期）
[root@test1 ~]#mysql -uroot -pxyy520
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.6.47 MySQL Community Server (GPL)
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
10:29:47(root@localhost) [(none)]> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
10:29:50(root@localhost) [test]>
测试结束。
同样方法，在mysql5.6上测试：
[root@test1 ~]#mysql -V
mysql Ver 14.14 Distrib 5.6.47, for linux-glibc2.12 (x86_64) using EditLine wrapper
##配置
vim /etc/my.cnf
[mysql]
prompt="\\r:\\m:\\s(\\u@\\h) [\\d]>\\_"
##测试（符合预期）
[root@test1 ~]#mysql -uroot -pxyy520
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.6.47 MySQL Community Server (GPL)
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
10:29:47(root@localhost) [(none)]> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
10:29:50(root@localhost) [test]>
2、配置字符集
字符集和排序😜
字符集命令汇总
- 早期MySQL版本默认为latin1，从MySQL8.0开始默认字符集已经为 utf8mb4，但前期版本一定要记得修改字符集，不然后期中文可能出现乱码；
- 推荐直接设置mysql全局，让其字符集为utf8mb4；
查看数据库支持的所有字符集：
SHOW CHARACTER SET;
查看当前数据库字符集的使用情况:
show variables like 'character%';
查看当前表使用的字符集：
show table status like 'student'\G
Collation: utf8_general_ci
或者查看创建表时的命令：
show create table student;
插入一条中文数据：
insert student (name,age)values('小彦彦',18);
删除一条中文数据：
delete from student where id=16;
select *from student;
设置表字符集：
ALTER TABLE student character set utf8mb4;
注意：
字符集相关文件：ll /usr/share/mysql/charsets/
`/data/mysql/test/db.opt `文件存放 了当前数据库苏使用的字符集
范例
- 查看数据库支持的所有字符集：
mysql> SHOW CHARACTER SET;
+----------+-----------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| swe7 | 7bit Swedish | swe7_swedish_ci | 1 |
| ascii | US ASCII | ascii_general_ci | 1 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci | 1 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci | 1 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| greek | ISO 8859-7 Greek | greek_general_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp866 | DOS Russian | cp866_general_ci | 1 |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci | 1 |
| macce | Mac Central European | macce_general_ci | 1 |
| macroman | Mac West European | macroman_general_ci | 1 |
| cp852 | DOS Central European | cp852_general_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| utf16 | UTF-16 Unicode | utf16_general_ci | 4 |
| utf16le | UTF-16LE Unicode | utf16le_general_ci | 4 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| utf32 | UTF-32 Unicode | utf32_general_ci | 4 |
| binary | Binary pseudo charset | binary | 1 |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci | 1 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
+----------+-----------------------------+---------------------+--------+
40 rows in set (0.01 sec)
mysql>
- 范例：字符集相关文件
[root@linux-test ~]#ll /usr/share/mysql/charsets/
total 232
-rw-r--r--. 1 root root 5526 Apr 20 2018 armscii8.xml
-rw-r--r--. 1 root root 5512 Apr 20 2018 ascii.xml
-rw-r--r--. 1 root root 8241 Apr 20 2018 cp1250.xml
-rw-r--r--. 1 root root 8365 Apr 20 2018 cp1251.xml
-rw-r--r--. 1 root root 5569 Apr 20 2018 cp1256.xml
-rw-r--r--. 1 root root 8902 Apr 20 2018 cp1257.xml
-rw-r--r--. 1 root root 5506 Apr 20 2018 cp850.xml
-rw-r--r--. 1 root root 5528 Apr 20 2018 cp852.xml
-rw-r--r--. 1 root root 5613 Apr 20 2018 cp866.xml
-rw-r--r--. 1 root root 6529 Apr 20 2018 dec8.xml
-rw-r--r--. 1 root root 5516 Apr 20 2018 geostd8.xml
-rw-r--r--. 1 root root 5728 Apr 20 2018 greek.xml
-rw-r--r--. 1 root root 5517 Apr 20 2018 hebrew.xml
-rw-r--r--. 1 root root 5502 Apr 20 2018 hp8.xml
-rw-r--r--. 1 root root 18307 Apr 20 2018 Index.xml
-rw-r--r--. 1 root root 5529 Apr 20 2018 keybcs2.xml
-rw-r--r--. 1 root root 5510 Apr 20 2018 koi8r.xml
-rw-r--r--. 1 root root 6532 Apr 20 2018 koi8u.xml
-rw-r--r--. 1 root root 9816 Apr 20 2018 latin1.xml
-rw-r--r--. 1 root root 7238 Apr 20 2018 latin2.xml
-rw-r--r--. 1 root root 5515 Apr 20 2018 latin5.xml
-rw-r--r--. 1 root root 7438 Apr 20 2018 latin7.xml
-rw-r--r--. 1 root root 8047 Apr 20 2018 macce.xml
-rw-r--r--. 1 root root 8058 Apr 20 2018 macroman.xml
-rw-r--r--. 1 root root 1749 Apr 20 2018 README
-rw-r--r--. 1 root root 6530 Apr 20 2018 swe7.xml
[root@linux-test ~]#
- 范例：
/data/mysql/test/db.opt文件存放了当前数据库苏使用的字符集
mysql> show variables like 'character%';
+--------------------------+----------------------------------------------------------------+
| Variable_name | Value |
+--------------------------+----------------------------------------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/local/mysql-5.6.47-linux-glibc2.12-x86_64/share/charsets/ |
+--------------------------+----------------------------------------------------------------+
8 rows in set (0.00 sec)
[root@test1 ~]#cat /data/mysql/test/db.opt
default-character-set=latin1
default-collation=latin1_swedish_ci
- 查看当前数据库字符集的使用情况:
mysql> show variables like 'character%';
+--------------------------+----------------------------------------------------------------+
| Variable_name | Value |
+--------------------------+----------------------------------------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/local/mysql-5.6.47-linux-glibc2.12-x86_64/share/charsets/ |
+--------------------------+----------------------------------------------------------------+
8 rows in set (0.00 sec)
mysql>
- 查看支持所有排序规则：
mysql> show COLLATION;
- 查看当前使用的排序规则
mysql> SHOW VARIABLES LIKE 'collation%';
+----------------------+-------------------+
| Variable_name | Value |
+----------------------+-------------------+
| collation_connection | utf8_general_ci |
| collation_database | latin1_swedish_ci |
| collation_server | latin1_swedish_ci |
+----------------------+-------------------+
3 rows in set (0.00 sec)
mysql>
- 范例：Mariadb10.3 默认的字符集(
latin1)和排序规则
MariaDB [(none)]> SELECT VERSION();
+-----------------+
| VERSION() |
+-----------------+
| 10.3.17-MariaDB |
+-----------------+
1 row in set (0.000 sec)
MariaDB [(none)]> show variables like 'character%';
+--------------------------+------------------------------+
| Variable_name | Value |
+--------------------------+------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mariadb/charsets/ |
+--------------------------+------------------------------+
8 rows in set (0.003 sec)
MariaDB [(none)]> SHOW VARIABLES LIKE 'collation%';
+----------------------+-------------------+
| Variable_name | Value |
+----------------------+-------------------+
| collation_connection | utf8_general_ci |
| collation_database | latin1_swedish_ci |
| collation_server | latin1_swedish_ci |
+----------------------+-------------------+
3 rows in set (0.001 sec)
- 范例：MySQL 8.0 默认的字符集(
utf8mb4)和排序规则
mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 8.0.17 |
+-----------+
1 row in set (0.00 sec)
mysql> show variables like 'character%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8mb4 |
| character_set_connection | utf8mb4 |
| character_set_database | utf8mb4 |
| character_set_filesystem | binary |
| character_set_results | utf8mb4 |
| character_set_server | utf8mb4 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.01 sec)
mysql> show variables like 'collation%';
+----------------------+--------------------+
| Variable_name | Value |
+----------------------+--------------------+
| collation_connection | utf8mb4_0900_ai_ci |
| collation_database | utf8mb4_0900_ai_ci |
| collation_server | utf8mb4_0900_ai_ci |
+----------------------+--------------------+
3 rows in set (0.00 sec)
范例：测试mysql5.6 数据库对中文的支持现象
- mysql5.6数据库：（默认是latin1字符集，插入中文数据时会报错）
##查看当前数据库字符集的使用情况:
mysql> show variables like 'character%';
character_set_client | utf8
character_set_server | latin1
##查看对应文件：
[root@test1 ~]#cat /data/mysql/test/db.opt
default-character-set=latin1
default-collation=latin1_swedish_ci
##创建一张新表
CREATE TABLE `student3` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
`age` tinyint(3) unsigned DEFAULT NULL,
`gender` enum('M','F') DEFAULT 'M',
PRIMARY KEY (`id`)
) ;
##插入一条中文数据
mysql> insert student3 (name,age,gender)values('小彦彦',18,'F');
ERROR 1366 (HY000): Incorrect string value: '\xE5\xB0\x8F\xE5\xBD\xA6...' for column 'name' at row 1
##查看表
mysql> select *from student3;
Empty set (0.00 sec)
- maridb-10.3数据库:（默认是latin1字符集，插入中文数据时会报 错）
##查看当前数据库字符集的使用情况:
08:37:18(root@localhost) [test]> show variables like 'character%';
character_set_client | utf8
character_set_server | latin1
##查看对应文件：
[root@test2 ~]#cat /var/lib/mysql/test/db.opt
default-character-set=latin1
default-collation=latin1_swedish_ci
##创建一张新表
CREATE TABLE `student3` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
`age` tinyint(3) unsigned DEFAULT NULL,
`gender` enum('M','F') DEFAULT 'M',
PRIMARY KEY (`id`)
) ;
##插入一条中文数据
08:38:53(root@localhost) [test]> insert student3 (name,age,gender)values('小彦彦',18,'F');
ERROR 1366 (22007): Incorrect string value: '\xE5\xB0\x8F\xE5\xBD\xA6...' for column `test`.`student3`.`name` at row 1
##查看表
08:38:59(root@localhost) [test]> select *from student3;
Empty set (0.000 sec)
- 但在其他的版本里，有可能是乱码：
- 因此，这里直接给mysql服务配置字符集为utf8mb4：
这里以mysql5.6为例子：
##1、查看当前使用的字符集
mysql> show variables like 'character%';
##2、设置
[root@linux-test ~]#vim /etc/my.cnf
[mysqld]
……
character-set-server=utf8mb4 #添加此行
[mysql]
default-character-set=utf8mb4
#重启mysql服务
systemctl restart mysqld
##3、确认（符合预期）
mysql> show variables like 'character%';
| character_set_client | utf8mb4
| character_set_server | utf8mb4
- 再次测试
##查看当前数据库字符集的使用情况:
mysql> show variables like 'character%';
character_set_client | utf8mb4
character_set_server | utf8mb4
##创建新数据库test2
create database test2;
##查看对应文件：
[root@test1 ~]#cat /data/mysql/test2/db.opt
default-character-set=utf8mb4
default-collation=utf8mb4_general_ci
##
use test2;
##创建一张新表
CREATE TABLE `student3` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
`age` tinyint(3) unsigned DEFAULT NULL,
`gender` enum('M','F') DEFAULT 'M',
PRIMARY KEY (`id`)
) ;
##插入一条中文数据
mysql> insert student3 (name,age,gender)values('小彦彦',18,'F');
Query OK, 1 row affected (0.00 sec)
##查看表:(符合预期)
mysql> select *from student3;
+----+-----------+------+--------+
| id | name | age | gender |
+----+-----------+------+--------+
| 1 | 小彦彦 | 18 | F |
+----+-----------+------+--------+
1 row in set (0.00 sec)
设置服务器默认的字符集
==🍊 实战：设置服务器默认的字符集-2024.4.22（测试成功）==
测试环境：5.6.47 MySQL Community Server
##1、查看当前使用的字符集
mysql> show variables like 'character%';
+--------------------------+----------------------------------------------------------------+
| Variable_name | Value |
+--------------------------+----------------------------------------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/local/mysql-5.6.47-linux-glibc2.12-x86_64/share/charsets/ |
+--------------------------+----------------------------------------------------------------+
8 rows in set (0.00 sec)
mysql>
##2、设置
[root@linux-test ~]#vim /etc/my.cnf
[mysqld]
……
character-set-server=utf8mb4 #添加此行
#重启mysql服务
systemctl restart mysqld
##3、确认（符合预期）
mysql> show variables like 'character%';
+--------------------------+----------------------------------------------------------------+
| Variable_name | Value |
+--------------------------+----------------------------------------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8mb4 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8mb4 |
| character_set_system | utf8 |
| character_sets_dir | /usr/local/mysql-5.6.47-linux-glibc2.12-x86_64/share/charsets/ |
+--------------------------+----------------------------------------------------------------+
8 rows in set (0.01 sec)
mysql>
设置mysql客户端默认的字符集
==🍊 实战：设置mysql客户端默认的字符集-2024.4.22（测试成功）==
测试环境：5.6.47 MySQL Community Server
##1、查看当前使用的字符集
mysql> show variables like 'character%';
+--------------------------+----------------------------------------------------------------+
| Variable_name | Value |
+--------------------------+----------------------------------------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/local/mysql-5.6.47-linux-glibc2.12-x86_64/share/charsets/ |
+--------------------------+----------------------------------------------------------------+
8 rows in set (0.00 sec)
mysql>
##2、设置
[root@linux-test ~]#vim /etc/my.cnf
[mysql]
……
default-character-set=utf8mb4 #添加此行
##3、确认（符合预期）
mysql> show variables like 'character%';
+--------------------------+----------------------------------------------------------------+
| Variable_name | Value |
+--------------------------+----------------------------------------------------------------+
| character_set_client | utf8mb4 |
| character_set_connection | utf8mb4 |
| character_set_database | utf8mb4 |
| character_set_filesystem | binary |
| character_set_results | utf8mb4 |
| character_set_server | utf8mb4 |
| character_set_system | utf8 |
| character_sets_dir | /usr/local/mysql-5.6.47-linux-glibc2.12-x86_64/share/charsets/ |
+--------------------------+----------------------------------------------------------------+
8 rows in set (0.01 sec)
mysql>
本次配置代码汇总
##1、查看当前使用的字符集
mysql> show variables like 'character%';
##2、配置
vim /etc/my.cnf
[mysqld]
character-set-server=utf8mb4 #添加此行
[mysql]
default-character-set=utf8mb4 #添加此行
##3、重启mysql服务
#重启mysql服务
systemctl restart mysqld
##4、测试
##查看当前数据库字符集的使用情况:
mysql> show variables like 'character%';
character_set_client | utf8mb4
character_set_server | utf8mb4
##创建新数据库test2
create database test2;
##查看对应文件：
[root@test1 ~]#cat /data/mysql/test2/db.opt
default-character-set=utf8mb4
default-collation=utf8mb4_general_ci
##
use test2;
##创建一张新表
CREATE TABLE `student3` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
`age` tinyint(3) unsigned DEFAULT NULL,
`gender` enum('M','F') DEFAULT 'M',
PRIMARY KEY (`id`)
) ;
##插入一条中文数据
mysql> insert student3 (name,age,gender)values('小彦彦',18,'F');
Query OK, 1 row affected (0.00 sec)
##查看表:(符合预期)
mysql> select *from student3;
+----+-----------+------+--------+
| id | name | age | gender |
+----+-----------+------+--------+
| 1 | 小彦彦 | 18 | F |
+----+-----------+------+--------+
1 row in set (0.00 sec)