For each document, list the number of employees who have showed up in the circulation history of that document. List the document ids and number of employees.
return documents ;return the   circulation history of   #1 ;return employees  who showed up in #2 ;return number of  #3 for each #1 ;return the   document  ids of   #1 ;return #5 ,  #4
['select', 'project', 'project', 'group', 'project', 'union']