SELECT a.month, SUM(b.total) AS total
FROM (
SELECT to_char(date("Joinin"),'YYYY-MM') AS month, SUM(sum) AS total
FROM (
SELECT Joinin, to_char(date("Joinin"),'YYYY-MM') AS month
, COUNT(*) AS sum
FROM "APP_HR_Staff_Basic_Info"
GROUP BY month
) ptuser
GROUP BY month
) a
JOIN (
SELECT to_char(date("Joinin"),'YYYY-MM') AS month, SUM(sum) AS total
FROM (
SELECT Joinin, to_char(date("Joinin"),'YYYY-MM') AS month
, COUNT(*) AS sum
FROM "APP_HR_Staff_Basic_Info"
GROUP BY month
) ptuser
GROUP BY month
) b
ON a.MONTH >= b.MONTH
GROUP BY a.MONTH
ORDER BY a.month;