https://m.blog.naver.com/PostView.naver?isHttpsRedirect=true&blogId=dev4unet&logNo=220602540023
select (SELECT COUNT(*) AS COUNT_DAYS_NO_WEEKEND
FROM GENERATE_SERIES ( ${frdate}::TIMESTAMP, ${todate}::TIMESTAMP, INTERVAL '1 DAY') THE_DAY
WHERE EXTRACT('ISODOW' FROM THE_DAY) < 7)::INTEGER -- 일요일 제외