Help!

127.0.0.1:3306 is a loopback, if you want to connect to the database on Railway then you need to use the host and port along with the credentials of the database you have deployed to Railway.

Even though I'm using data from the mysql.railway.internal DB, I'm still unable to connect. Which items exactly should I use from the variable list?

Even though I'm using data from the mysql.railway.internal DB, I'm still unable to connect. Which items exactly should I use from the variable list?

you need to use the public host and port from the service settings under public networking.

https://docs.railway.com/overview/the-basics#service-settings

Strangely, it's not working.

If I use "MYSQLHOST" as "mysql.railway.internal" the error message is "Unable to connect to mysql.railway.internal:3306". If I use "MYSQL_URL" as "mysql://root:oleJuELIRUlOVtxmGmopWDqBmpiXZCdR@mysql.railway.internal:3306/railway" the error message is "Invalid hostname URL.".

Per my previous message, you need to use the public host and port.

I believe I am using the correct references as marked "in red" in the attached image.

Wouldn't these be it?

No, those are the private host and port variables.

Please see my previous message.