What are all the distinct last names of all the engineers?
SELECT DISTINCT last_name FROM Maintenance_Engineers
SELECT DISTINCT last_name FROM Maintenance_Engineers
[{'last_name': 'Reinger'}, {'last_name': 'Orn'}, {'last_name': 'Hauck'}, {'last_name': 'Morar'}, {'last_name': 'Grady'}, {'last_name': 'Adams'}, {'last_name': 'Harvey'}, {'last_name': 'Hirthe'}, {'last_name': 'Stamm'}, {'last_name': 'Price'}, {'last_name': 'Kunde'}, {'last_name': 'Simonis'}, {'last_name': 'Hahn'}, {'last_name': 'Goldner'}, {'last_name': 'Streich'}]