How many employees are there?
select count ( * ) from employees
How many employees are in the circulation history with the document id 1?
select count ( employee_id ) from circulation_history where document_id = 1
Can you tell me the name of the employee that is in the circulation history with document id 1?
select t1.employee_name from employees as t1 join circulation_history as t2 on t1.employee_id = t2.employee_id where t2.document_id = 1