How many engineers did each staff contact? List both the contact staff name and number of engineers contacted.
SELECT T1.staff_name ,  count(*) FROM Staff AS T1 JOIN Engineer_Visits AS T2 ON T1.staff_id  =  T2.contact_staff_id GROUP BY T1.staff_name
number of engineers contacted refers to COUNT(*); list both the staff name and number of engineers refers to SELECT T1.staff_name, COUNT(*) and GROUP BY T1.staff_name;