How to recover MySQL database from .myd, .myi, .frm files

If these are MyISAM tables, then plopping the .FRM, .MYD, and .MYI files into a database directory (e.g., /var/lib/mysql/dbname) will make that table available. It doesn't have to be the same database as they came from, the same server, the same MySQL version, or the same architecture. You may also need to change ownership for the folder (e.g., chown -R mysql:mysql /var/lib/mysql/dbname)

Note that permissions (GRANT, etc.) are part of the mysql database. So they won't be restored along with the tables; you may need to run the appropriate GRANT statements to create users, give access, etc. (Restoring the mysql database is possible, but you need to be careful with MySQL versions and any needed runs of the mysql_upgrade utility.)

Actually, you probably just need the .FRM (table structure) and .MYD (table data), but you'll have to repair table to rebuild the .MYI (indexes).

The only constraint is that if you're downgrading, you'd best check the release notes (and probably run repair table). Newer MySQL versions add features, of course.

[Although it should be obvious, if you mix and match tables, the integrity of relationships between those tables is your problem; MySQL won't care, but your application and your users may. Also, this method does not work at all for InnoDB tables. Only MyISAM, but considering the files you have, you have MyISAM]

You can copy the files into an appropriately named subdirectory directory of the data folder as long as it is the EXACT same version of mySQL and you have retained all of the associated files in that directory. If you don't have all the files, I'm pretty sure you're going to have issues.