Question: which engineer made the least number of visits? | Here are the id, first, and last names of the engineer who has the least number of visits. | how many visits did each engineer have?
SQL: SELECT count ( * ) ,T1.engineer_id FROM Maintenance_Engineers AS T1 JOIN Engineer_Visits AS T2 ON T1.engineer_id   =   T2.engineer_id GROUP BY T1.engineer_id