How to "Connect to an existing database" from powershell

[#1]

I'm preparing migration script, and since there is a lot of different problems, we would like to automate migration as much as possible.

So one of the thing during migration, is that we have to open central administration and we would prefer to skip this, and just do it with powershell.

So how can we attach existing Configuration Database with use of powershell?

[#2]

You have an excellent script of Matthew Yarlett, who can be a great input for your automation: Matthew Yarlett: Provisioning a new Nintex Workflow Content Database using PowerShell Instead of provisioning you can attach your DBs