To install MySQL 5.7, you should enable MySQL 5.7 community release yum repository on your system.


STEP 1. Enable MySQL Repository

yum localinstall https://dev.mysql.com/get/mysql57-community-release-el7-9.noarch.rpm


STEP 2. Install MySQL 5.7 Server

yum install mysql-community-server


STEP 3. Start MySQL Service

service mysqld start


STEP 4. Checking temporary password

grep 'A temporary password' /var/log/mysqld.log | tail -1

Then you will be able to see its result like below:

2020-04-20T01:50:07.931468Z 1 [Note] A temporary password is generated for root@localhost: #l+wu>PMv7vJ



STEP 5. Initial MySQL Configuration

/usr/bin/mysql_secure_installation

Note you can use the temporary password acquired at STEP 4.