How to connect one docker project to another docker project database

So I have two docker projects in local development one running a MySQL database and the other not running any MySQL. How do you connect the docker project without a database to the one that has the database?

I used direct connection and added all the credentials from the project running the database. I test the connection it said ok. But once I created an insert form in the none database project and actually tried to submit the form with some data I got a 500 response which is leading me think maybe that’s not quite possible on local development. Can someone explain to me what I am missing or how to accomplish this task. Thanks.

@Teodor @George @ben