ActiveRecord OR clause in scoped query

问题

statuses = %w(sick healthy hungry)

query = User.scoped(:joins => 'left outer join pets on pets.user_id = users.id', :conditions => { 'pets.id' => nil, 'users.job_status' => stati })

Given the code above, is it possible to add an OR clause to the :conditions to say something like

where (pets.id is NULL AND users.status IN ('sick', 'healthy', 'hungry')) OR (users.gender = 'male')

回答1:

You can do the following using the MetaWhere gem

statuses = %w(sick healthy hungry)

query = User.include(:pets).where(
  ('pets.id' => nil, 'users.job_status' => statuses) |
  ('users.gender' => 'male')
)

The | symbol is used for OR condition.

PS : The include directive uses LEFT OUTER JOIN so there is no need to hand code the JOIN.

回答2:

You could use an SQL condition instead of a Hash condition:

query = User.scoped(
    :joins => 'left outer join pets on pets.user_id = users.id',
    :conditions => [
        '(pets.id is null AND users.status IN (?)) OR (users.gender = ?)',
        statuses, 'male'
    ]
)

Or:

query = User.scoped(
    :joins => 'left outer join pets on pets.user_id = users.id',
    :conditions => [
        '(pets.id is null AND users.status IN (:statuses)) OR (users.gender = :gender)',
        { :status => statuses, :gender => 'male' }
    ]
)

The downside is that you have to avoid trying pets.is = NULL by hand.

来源：https://stackoverflow.com/questions/7535592/activerecord-or-clause-in-scoped-query