sql - Count records which has no association or association of association meets condition -

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assume have 3 classes:

class person   belongs_to :group end  class group   has_many :people   has_many :tags end  class tag   belongs_to :group end

it possible, person may have group_id = null.

what need, count person records has group_id = null or group doesn't have tag record attribute status in ('active', 'finished')

one more thing, has fast possible. querying on milions of records.

ideas? thanks.


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