Even when you're not using it for your app, sequel + irb make a nice database repl, especially useful if you want to transform and analyze some data with Ruby methods or need to work with several databases at once.
Yes, multiple databases are really useful for me, for some reason I often need to transfer data from one to another, e.g. legacy database to a new improved one (which I think happens often if you're in a non-startup).
In ActiveRecord you would have to specify for each model to which the database to connect. And then you have to figure out how to call a User model in one database, and how in the other (you have to call them differently, even if table names are the same). I think it can get pretty chaotic with something bigger.
I don't do Ruby anymore, but back when I first started I did a little side project with Sinatra and Sequel and definitely enjoyed it over ActiveRecord. As another user said, now that I'm a Python programmer, I have always been drawn to SQLAlchemy in a similar way.
As someone who is just dipping my toes into Rails (but has used plenty of other ORMs in other languages): ActiveRecord doesn't have native left join support?!
I'm really glad I came across this before starting my first Rails project. Thanks for the post!
SQLAlchemy does have the issue that, as far as I know, you can't use it "entity-less": you always need to have Table and Column objects instantiated (possibly via reflection, but still…). That you can use sequel solely for query building without needing any kind of backing objects is neat.
