Rails: ActiveRecord query regarding size of association -


i'm trying figure out how produce query, using activerecord.

i have following models

class activity < activerecord::base   attr_accessible :limit, ...         has_many :employees end  class user < activerecord::base   belongs_to :activity end

each activity has limit, say, integer attribute containing maximum amount of users may belong it.

i'm looking way select activities have spots available, i.e. number of users smaller limit.

any ideas?

thanks

i think sql syntax aim be:

select *   activities  activities.limit > (          select count(*)            users           users.activity_id = activities.id)

in rails-speak ...

activity.where("activities.limit > (select count(*) users users.activity_id = activities.id)")

not sure whether column name "limit" going give problems it's reserved word. might have quote in sql.

i'd consider counter cache users on activities table, make perform better. databases support partial index rows users counter cache < limit.


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