sql - 使用动态查找器指定 NOT NULL

Question

我经常想使用动态查找器来指定 NOT NULL。所以……

这个有效:

Widget.find_all_by_color('blue')

这个有效:

Widget.find_all_by_color(nil)

可是我该怎么办

SELECT * FROM `widgets` WHERE `color` IS NOT NULL;

?

Answer 1

两种方式取决于你想要的具体程度:

# in your model
class Widget < ActiveRecord::Base
  # first way
  named_scope :coloured, {:conditions => ["color IS NOT NULL"]}
  # second way
  named_scope :not_null, lambda{|*args| (field=args.first ? {:conditions => ["#{field} is not null",field]} : {}) } }
end

# in your controller
@coloured_widgets = Widget.coloured.all           # using first way
@coloured_widgets = Widget.not_null(:colour).all  # using second way

希望对你有帮助。

干杯