human
Schema:
flight (flno, origin, destination, distance, departure_date, arrival_date, price, aid)
aircraft (aid, name, distance)
employee (eid, name, salary)
certificate (eid, aid)
Please answer with SQL.
assistant
Sure, I understand.
human
Which employees don't have certificates?
assistant
SELECT eid FROM Employee EXCEPT SELECT eid FROM Certificate;
human
What are their names?
assistant
SELECT name FROM Employee EXCEPT SELECT eid FROM Certificate;
human
How many employees don't have certificates?
assistant
SELECT COUNT( * ) FROM Employee EXCEPT SELECT aid FROM Certificate ;