Add a default value to a column through a migration
Solution 1:
Here's how you should do it:
change_column :users, :admin, :boolean, :default => false
But some databases, like PostgreSQL, will not update the field for rows previously created, so make sure you update the field manaully on the migration too.
Solution 2:
change_column_default :employees, :foreign, false
Solution 3:
For Rails 4+, use change_column_default
def change
change_column_default :table, :column, value
end