Question

This query won’t return any records, when hidden_episodes_ids is empty.

:conditions => ["episodes.show_id in (?) AND air_date >= ? AND air_date <= ? AND episodes.id NOT IN (?)", @show_ids, @start_day, @end_day, hidden_episodes_ids]

If it’s empty, the SQL will look like NOT IN (null)

So my solution is:

if hidden_episodes_ids.any?
    *mode code*:conditions => ["episodes.show_id in (?) AND air_date >= ? AND air_date <= ? AND episodes.id NOT IN (?)", @show_ids, @start_day, @end_day, hidden_episodes_ids]
else
    *mode code*:conditions => ["episodes.show_id in (?) AND air_date >= ? AND air_date <= ?", @show_ids, @start_day, @end_day]
end

But it is rather ugly (My real query is actually 5 lines, with joins and selects etc..)

Is there a way to use a single query and avoid the NOT IN (null)?

PS: These are old queries migrated into Rails 3, hence the :conditions

Answer 1

You should just use the where method instead as that’ll help clean all of this up. You just chain it together:

scope = Thing.where(:episodes => { :show_id => @show_ids })
scope = scope.where('air_date BETWEEN ? AND ?', @start_day, @end_day)

if (hidden_episode_ids.any?)
  scope = scope.where('episodes.id NOT IN (?)', hidden_episode_ids)
end

Being able to conditionally modify the scope avoids a lot of duplication.