If one of the carriages is pulled by a single horse.
return carriages ;return horses ;return #1 pulled by #2 ;return number of  #2 for each  #3 ;return #3 where  #4 is equal to  one ;return number of  #5 ;return if  #6 is equal to  one
['select', 'select', 'filter', 'group', 'comparative', 'aggregate', 'boolean']