Rails迁移没有提供任何添加约束的方法，但是您仍然可以通过迁移来实现，但只需将实际的SQL传递给execute()

Rails migration does not provide any way to add Constraints, but you can still do it via migration but by passing actual SQL to execute()

创建迁移文件:

ruby script/generate Migration AddConstraint

现在，在迁移文件中:

class AddConstraint < ActiveRecord::Migration
  def self.up
    execute "ALTER TABLE table_name ADD CONSTRAINT check_constraint_name CHECK (check_column_name IN (1, 2, 3) )"
  end

  def self.down
    execute "ALTER TABLE table_name DROP CONSTRAINT check_constraint_name"
  end
end