Querying

delegate :find, :take, :take!, :first, :first!, :last, :last!, :exists?, :any?,
         :many?, to: :all
delegate :second, :second!, :third, :third!, :fourth, :fourth!, :fifth, :fifth!,
         :forty_two, :forty_two!, to: :all
delegate :first_or_create, :first_or_create!, :first_or_initialize, to: :all
delegate :find_or_create_by, :find_or_create_by!, :find_or_initialize_by, to: :all
delegate :find_by, :find_by!, to: :all
delegate :destroy, :destroy_all, :delete, :delete_all, :update, :update_all, to: :all
delegate :find_each, :find_in_batches, to: :all
delegate :select, :group, :order, :except, :reorder, :limit, :offset, :joins, :where,
         :rewhere, :preload, :eager_load, :includes, :from, :lock, :readonly, :having,
         :create_with, :uniq, :distinct, :references, :none, :unscope, to: :all
delegate :count, :average, :minimum, :maximum, :sum, :calculate, to: :all
delegate :pluck, :ids, to: :all

除上述 delegate 方法外，还有：

find_by_sql

count_by_sql