mysqlでint方の年・月・日をdateに変換して、現在日よりを求める

SELECT CAST(concat(year,'-',month,'-',day) AS DATE) FROM `tbl_calendar` WHERE CAST(concat(LPAD(year, 4, '0'),'-',LPAD(month, 2, '0'),'-',LPAD(day, 2, '0')) AS DATE) >= CURDATE()