Issue with composite datasets not returning a reversed iterator.

This results in tables being truncated in the same order they are created which in my case caused numerous foreign key issues.

Whilst creating the test for this I noticed some issues with the MySQL test setup which I have also updated.
Without a separate variable if a sqllite connection had been previously created the condition around the mysql connection creation was not truthy.

So as to not have to recreate connections as the database under test alternates.