How to correctly install mysql server 5.7 so that mysql-common does not upgrade to 5.8?

Question

linux

Hello.
Debian 9.12
VPS on selectel.ru
Only selectel.ru repositories are in /etc/apt/sources.list.

It was required to install mysql 5.7 server. I downloaded mysql-apt-config_0.8.15-1_all.deb from the official site and installed it.
When installing mysql server version 5.7, for some reason it pulled the mysql-common package from the selectel.ru repository (mysql-common/oldstable 5.8+1.0.2 amd64).
As a result, after installation, almost all installed packages were 5.7 (from the repo.mysql.com repository), and mysql-common version was 5.8 (from mirror.selectel.ru).

After removing everything installed, I first had to manually install mysql-common version 5.7 and freeze it to upgrade
apt install mysql-common=5.7.30-1debian9
apt-mark hold mysql-common=5.7.30-1debian9

And only after that install mysql-server.
As a result, we get the inability to upgrade the mysql-common package in the future, which is very inconvenient and not correct.

Please tell me how to solve this problem correctly, that all versions were 5.7?
Removing all entries from mirror.selectel.ru from /etc/apt/sources.list and installing the standard ones ( https://wiki.debian.org/ru/SourcesList ) from debian.org? Or some other way?
Thank you.

Answer 1

as I understand mysql-common version 5.8 is normal for mysql-server 5.7
There is nothing strange about this.
If not, please correct.