The MySQL.Ru manual states that you can name tables and columns using different characters (in earlier versions _ , $ ). Should I use or be limited to _ ?
2 answers
Such things should be stipulated in the "coding standard" of a specific development team. What is normal for some is a nightmare. It is important that in one project there is no diversity in this plan.
In those places where I had to work, for MySQL names it was customary to limit itself to the lower case Latin + numbers and underscore, snake-syntax.
Here are some explanatory naming conventions:
http://anandarajpandey.com/2015/05/10/mysql-naming-coding-conventions-tips-on-mysql-database/
https://raw.githubusercontent.com/treffynnon/sqlstyle.guide/gh-pages/_includes/sqlstyle.guide.md
I recommend to use: lower case, letters, numbers and underscore.
This is the most common variant in the popular FW.
For the community PHP + MySQL, IMHO, is already standard.
The fewer non-standard solutions, the more flexible and safer.
_- safer. - cyadvert$? - Kromster