SQL wp_db plus external db

I’m integrating external php files which use a separate database.

So in my various files, I’m including the external database connect string. I don’t have any problem pulling in current user data to these files, but I want to query the wp_users table with SQL as well.

it appears that I don’t have access to the wp_users table as my connect string for the other database has knocked it out.

Anyone tried to do the same ?