https://www.bilibili.com/video/BV1Sv411r7vd?p=89

1.新建文件夹/opt/mysql，并cd进去

mkdir /opt/mysql
cd /opt/mysql/

2. 运行 wget http://dev.mysql.com/get/mysql-5.7.26-1.el7.x86_64.rpm-bundle.tar ，下载mysql安装包

PS：centos7.6自带的类mysql数据库是mariadb，会跟mysql冲突，要先删除。

3. 运行 tar -xvf mysql-5.7.26-1.el7.x86_64.rpm-bundle.tar

4. 运行 rpm -qa|grep mari ，查询 mariadb 相关安装包

5. 运行 rpm -e --nodeps mariadb-libs 和 rpm -e --nodeps marisa ，卸载

[root@cjbCentos01 mysql]# rpm -qa|grep mari
mariadb-libs-5.5.68-1.el7.x86_64
marisa-0.2.4-4.el7.x86_64
[root@cjbCentos01 mysql]# rpm -e --nodeps mariadb-libs
[root@cjbCentos01 mysql]# rpm -qa|grep mari
marisa-0.2.4-4.el7.x86_64
[root@cjbCentos01 mysql]# rpm -e --nodeps marisa

再次查看没有 mariadb 的相关安装包

6. 然后开始真正安装mysql，依次运行以下几条

rpm -ivh mysql-community-common-5.7.26-1.el7.x86_64.rpm
rpm -ivh mysql-community-libs-5.7.26-1.el7.x86_64.rpm
rpm -ivh mysql-community-client-5.7.26-1.el7.x86_64.rpm
rpm -ivh mysql-community-server-5.7.26-1.el7.x86_64.rpm

案例:

[root@cjbCentos01 mysql]# rpm -ivh mysql-community-common-5.7.26-1.el7.x86_64.rpm
警告：mysql-community-common-5.7.26-1.el7.x86_64.rpm: 头V3 DSA/SHA1 Signature, 密钥 ID 5072e1f5: NOKEY
准备中...                          ################################# [100%]
正在升级/安装...
   1:mysql-community-common-5.7.26-1.e################################# [100%]
[root@cjbCentos01 mysql]# rpm -ivh mysql-community-libs-5.7.26-1.el7.x86_64.rpm
警告：mysql-community-libs-5.7.26-1.el7.x86_64.rpm: 头V3 DSA/SHA1 Signature, 密钥 ID 5072e1f5: NOKEY
准备中...                          ################################# [100%]
正在升级/安装...
   1:mysql-community-libs-5.7.26-1.el7################################# [100%]
[root@cjbCentos01 mysql]# rpm -ivh mysql-community-client-5.7.26-1.el7.x86_64.rpm

警告：mysql-community-client-5.7.26-1.el7.x86_64.rpm: 头V3 DSA/SHA1 Signature, 密钥 ID 5072e1f5: NOKEY
准备中...                          ################################# [100%]
正在升级/安装...
   1:mysql-community-client-5.7.26-1.e################################# [100%]
[root@cjbCentos01 mysql]# 
[root@cjbCentos01 mysql]# rpm -ivh mysql-community-server-5.7.26-1.el7.x86_64.rpm
警告：mysql-community-server-5.7.26-1.el7.x86_64.rpm: 头V3 DSA/SHA1 Signature, 密钥 ID 5072e1f5: NOKEY
准备中...                          ################################# [100%]
正在升级/安装...
   1:mysql-community-server-5.7.26-1.e################################# [100%]
[root@cjbCentos01 mysql]# 

7.运行 systemctl start mysqld.service ，启动mysql

8. 然后开始设置root用户密码
Mysql自动给root用户设置随机密码，运行 grep “password” /var/log/mysqld.log 可看到当前密码
案例:

[root@cjbCentos01 mysql]# grep "password" /var/log/mysqld.log
2021-10-01T10:09:39.951331Z 1 [Note] A temporary password is generated for root@localhost: b+IOpn<r5dk/
[root@cjbCentos01 mysql]# 

9.运行 mysql -u root -p ，用root用户登录，提示输入密码可用上述的，可以成功登陆进入mysql命令行

10. 设置root密码，对于个人开发环境，要设比较简单的密码（生产环境服务器要设复杂密码），可以运行
set global validate_password_policy=0; 提示密码设置策略
（validate_password_policy默认值1，）
查看数据库当前的密码策略: show VARIABLES like “%password%”;

mysql> show VARIABLES like "%password%";
+---------------------------------------+-------+
| Variable_name                         | Value |
+---------------------------------------+-------+
| default_password_lifetime             | 0     |
| disconnect_on_expired_password        | ON    |
| log_builtin_as_identified_by_password | OFF   |
| mysql_native_password_proxy_users     | OFF   |
| old_passwords                         | 0     |
| report_password                       |       |
| sha256_password_proxy_users           | OFF   |
| validate_password_check_user_name     | OFF   |
| validate_password_dictionary_file     |       |
| validate_password_length              | 8     |
| validate_password_mixed_case_count    | 1     |
| validate_password_number_count        | 1     |
| validate_password_policy              | MEDIUM|
| validate_password_special_char_count  | 1     |
+---------------------------------------+-------+
14 rows in set (0.00 sec)

set global validate_password_length=0; 更改密码长度
案例:

mysql> set global validate_password_policy=0;  # 更改密码策略为LOW,只要求长度(默认8位)
Query OK, 0 rows affected (0.00 sec)

mysql> set password for 'root'@'localhost' =password('123456');
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
mysql> set global validate_password_length=0; # 更改密码长度
Query OK, 0 rows affected (0.00 sec)

11 设置root密码 set password for ‘root’@‘localhost’ =password(‘123456’);

12. 运行 flush privileges; 使密码设置生效

13. 退出MySQL命令行（可使用\q、QUIT或EXIT），使用新密码登录