Если вам нужны все детали, то:
SELECT ssn,
employee_id,
is_active
FROM (
SELECT ssn,
employee_id,
is_active,
COUNT( DISTINCT employee_id ) OVER ( PARTITION BY ssn ) AS num_emps,
COUNT( CASE is_active WHEN 'Y' THEN 1 END ) OVER ( PARTITION BY ssn )
AS num_active
FROM employee
)
WHERE num_emps > 1
AND num_active > 0
Если вы просто хотите ssn
s, тогда:
SELECT ssn
FROM employee
GROUP BY ssn
HAVING COUNT( DISTINCT employee_id ) > 1
AND COUNT( CASE is_active WHEN 'Y' THEN 1 END ) > 0;