How to exclude an array of ids from query in Rails (using ActiveRecord)?

问题

I would like to perform an ActiveRecord query that returns all records except those records that have certain ids. The ids I would like excluded are stored in an array. So:

ids_to_exclude = [1,2,3]
array_without_excluded_ids = Item. ???

I'm not sure how to complete the second line.

Background: What I've already tried:

I'm not sure background is necessary, but I've already tried various combinations of .find and .where. For example:

array_without_excluded_ids = Item.find(:all, :conditions => { "id not IN (?)", ids_to_exclude })
array_without_excluded_ids = Item.where( "items.id not IN ?", ids_to_exclude)

These fail. This tip might be on the right track, but I have not succeeded in adapting it. Any help would be greatly appreciated.

回答1:

This should work:

ids_to_exclude = [1,2,3]
items_table = Arel::Table.new(:items)

array_without_excluded_ids = Item.where(items_table[:id].not_in ids_to_exclude)

And it's fully object-oriented with no strings :-)

回答2:

Rails 4 solution:

ids_to_exclude = [1,2,3]
array_without_excluded_ids = Item.where.not(id: ids_to_exclude)

回答3:

You can also use Squeel gem to accomplish such query. Documentation of it, goes here

来源：https://stackoverflow.com/questions/4581376/how-to-exclude-an-array-of-ids-from-query-in-rails-using-activerecord