Question

create table foo (id, name, order, ...);
create table foo_bar (id, foo_id, name, value);

foo contains order column with values as (1,2,3,4,5,…10)
assuming foo_bar contains multiple records for each foo.

How do I delete foos whose order values are 3..6 and its dependent records?

Answer 1

class Foo < ActiveRecord::Base
  has_many :foo_bars,  :dependent => :destroy
end

class FooBar < ActiveRecord::Base
  belongs_to  :foo
end

If your relation is like above following code will work

Foo.delete_all(["id in (?)", [3,4,5,6]])

OR Just

Foo.delete([3,4,5,6])

Ref delete

EDITED

From little i know your question i think you have something like following

foo table

id  some_column    order
1   some_value      3
2   some_value      4
3   some_value      3
4   some_value      2
5   some_value      1
6   some_value      5
7   some_value      6

foo_bar table

id  some_column    foo_id
1   some_value      2
2   some_value      1
3   some_value      3
4   some_value      2
5   some_value      4
6   some_value      5
7   some_value      6

Then user following order instead of id

Foo.delete_all(["order in (?)", [3,4,5,6]])

EDITED: Use destroy_all to Destroys the records by instantiating each record and calling its {#destroy}[rdoc-ref:Persistence#destroy] method.

Foo.destroy_all(["order in (?)", [3,4,5,6]])