Relationships

How does one setup relations between table

I have the has_many and belongs_to in the correct places (hopefully) but
i think i have the migrations in the incorrect order

A user can create many jobs
so i have

user has_many jobs
and jobs belongs_to user

however i have the migration that creates the job table before i have
the migration that creates the user table can i still get this to work
and if not,
How does one change the order of the migration with deleting the first
one and creating it again

and does the migration need to have t.column user_id, :int or will this
be added automatically