WITH t1 AS
(
SELECT 300000 cnt
)
, t2 AS
(
SELECT 1 seq, 1 start, 100000 ends, 5.0 cals
UNION ALL SELECT 2, 100001,  300000, 4.8
UNION ALL SELECT 3, 300001, 1000000, 4.6
)
SELECT SUM((LEAST(b.ends, a.cnt) - b.start + 1) * b.cals) x
  FROM t1 a
 INNER JOIN t2 b
    ON a.cnt >= b.start
;

마농님 

역시 한방에 해결해주시네요..너무 너무 감사합니다.

밥한번 사고 싶을 만큼요