Changing the database from mysql to sqlite3 - need help

As far as I know, the only thing you need to change is database.yaml.
So I set up it, changing adapter from mysql to sqlite and pointing to
the file, which should play a role of database. Now when I try to run
rake db:create an error pops up saying "Could not find table 'users'".
Why's that and how to override this? By logic, db:create is only
creating a blank database, without any table in it. So, what's the
deal with tables then?

Thanks

I found solution.

The reason why rake aborted was that the environment.rb had some
observers set up. It seems that these observers tried to communicate
with a model, which table had not been created. That's how it should
be though - you can't have a table for a model in the database, if you
don't have the database. And the error occurred when I was trying to
run rake db:create. So, it seems now that the only solution is to
comment observers in the environment.rb before creating the database
and comment them when the database is created, which is a little
stupid - who knows how much times I would need to drop database and
create it again and now I need to comment and uncomment observers each
time?

Does anyone know better solution?
Thanks