migration issue

This would suggest that the migration you were running was attempting to add the artists table. I think this is nothing to do with rake db:sessions:create. Have a look in the migration made by the rake to see what it is doing. I imagine that you have an earlier migration that created the artists table and for some reason that is running again.

Colin

Also, check the schema_migrations table in your database to see what
migration it thinks you last ran.