SELECT document_id ,  count(DISTINCT employee_id) FROM Circulation_History GROUP BY document_id;
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.
SELECT document_id , count ( DISTINCT employee_id ) FROM Circulation_History GROUP BY document_id ;
select document_id , count ( distinct employee_id ) from circulation_history group by document_id
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 .