第一章 MySQL的安装和配置

Ubuntu 18.04 安装 mysql 的过程中，竟然没有让你输入秘密？！（之前在 Ubuntu 14.04 下，安装过程中会询问密码），这导致安装完 mysql 初始秘密不知道的问题。

sudo apt-get install mysql-server-5.7

解决方法如下：

1）安装完成后，会生成文件 /etc/mysql/debian.cnf ，初始用户名和秘密如下 (这里密码是随机的)

sudo cat /etc/mysql/debian.cnf 

# Automatically generated for Debian scripts. DO NOT TOUCH!
[client]
host     = localhost
user     = debian-sys-maint
password = 63vIY3PtyKh10cmZ
socket   = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host     = localhost
user     = debian-sys-maint
password = 63vIY3PtyKh10cmZ
socket   = /var/run/mysqld/mysqld.sock

2）使用这个用户名和秘密登陆 mysql

$ mysql -h 127.0.0.1 -u debian-sys-maint -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.26-0ubuntu0.18.04.1 (Ubuntu)
Copyright (c) 2000, 2019, 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.
mysql> 

3）然后做如下操作（这里设置秘密为 1，读者请自行设置自己的密码）

mysql> update mysql.user set authentication_string=password('1') where user='root' and host='localhost';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1

mysql> update user set plugin='mysql_native_password';
Query OK, 1 row affected (0.00 sec)
Rows matched: 4  Changed: 1  Warnings: 0

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> quit;
Bye

4）重新启动 mysql

sudo service mysql restart

5）之后就可以使用 root 登陆了

    $ mysql -h 127.0.0.1 -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.26-0ubuntu0.18.04.1 (Ubuntu)

Copyright (c) 2000, 2019, 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.

mysql> 

6）检查默认字符编码

    mysql> show variables like 'character_set_%';
+--------------------------+----------------------------+
| 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/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

　　将其改为 utf8，打开 /etc/mysql/mysql.conf.d/mysqld.cnf，在最后添加一句，

character-set-server=utf8

sudo vim /etc/mysql/conf.d/mysql.cnf 命令打开mysql.cnf配置文件，添加代码：

default-character-set=utf8 

　　重新启动 mysql，

sudo service mysql restart

　　再次查看字符编码，

mysql> show variables like 'character_set_%';
+--------------------------+----------------------------+
| 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 (0.01 sec)

7）使用 mycli 自动补全

默认 mysql 命令行登陆后，输入命令不会提示及自动补全，非常麻烦，通过使用 mycli 自动补全会方便很多。

安装如下，

sudo pip install -i https://pypi.tuna.tsinghua.edu.cn/simple/ mycli

使用 mycli 启动数据库连接，

mycli -h 127.0.0.1 -u root -p ******** ( here your DB password)

参考