Usar:
SELECT SUM(CASE WHEN p.problem_type = 'IN' THEN 1 ELSE 0 END) AS IN,
SUM(CASE WHEN p.problem_type = 'OUT' THEN 1 ELSE 0 END) AS OUT,
TO_CHAR(datetime, 'YYYY') AS year,
TO_CHAR(datetime, 'MM') AS month
FROM PROBLEM p
WHERE p.DateTime >= TO_DATE('2010-01-01', 'YYYY-MM-DD')
AND p.DateTime < TO_DATE('2010-01-31', 'YYYY-MM-DD')
GROUP BY TO_CHAR(datetime, 'YYYY'), TO_CHAR(datetime, 'MM')
También podrías usar:
SELECT SUM(CASE WHEN p.problem_type = 'IN' THEN 1 ELSE 0 END) AS IN,
SUM(CASE WHEN p.problem_type = 'OUT' THEN 1 ELSE 0 END) AS OUT,
TO_CHAR(datetime, 'MM-YYYY') AS mon_year
FROM PROBLEM p
WHERE p.DateTime >= TO_DATE('2010-01-01', 'YYYY-MM-DD')
AND p.DateTime < TO_DATE('2010-01-31', 'YYYY-MM-DD')
GROUP BY TO_CHAR(datetime, 'MM-YYYY')
Referencia:
