🟢 Solve problem 1789

Author: AF2B

sql/1789.sql

@@ -0,0 +1,9 @@
+SELECT employee_id, department_id
+FROM Employee
+WHERE primary_flag = 'Y'
+   OR employee_id IN (
+       SELECT employee_id
+       FROM Employee
+       GROUP BY employee_id
+       HAVING COUNT(*) = 1
+   );