Change Column Null

The not null constraint is a great way to ensure data integrity. If a Rails model validates_presence_of an attribute, that column should be not null in the database.

Rails has a special migration method for setting this constraint.

change_column_null :users, :mandatory_attribute, false

You could also use the change_column method. The reason change_column_null is a better choice is that change_column requires you to state the type of the column; change_column_null does not.

change_column(table_name, column_name, type, options)
change_column_null(table_name, column_name, null, default = nil)