Relating 2 database?

i know about working with 2 tables in database now is it a good idea or even possible to relate 2 databases ?

I’m trying to integrate 2 modules who has different databases and different login system. Now there will be only one login for them. Should/can I keep 2 databases or should I extract or create new tables in the parent database?


This is more of a question of what your two different database engines are. If you are able to create a symbolic lonk between the two databases, that may be the way to go. How heavy will you be querying across both?