수량을 80% / 20% 로 나누는게 맞나요?

2/6 과 4/6 으로 나눠야 하는거 아닐지....

WITH 테이블 AS (
  SELECT '1' AS 키값, 2521 AS 수량 UNION ALL
  SELECT '2' AS 키값, 2220 AS 수량   
),
임시테이블 AS (
 SELECT '1' AS RN, 2 AS AMT UNION ALL  
 SELECT '2' AS RN, 2 AS AMT UNION ALL  
 SELECT '3' AS RN, 2 AS AMT 
)
,TEMP AS (
SELECT T1.키값, T2.RN
,T1.수량
,T1.수량 * (T2.AMT / SUM(T2.AMT) OVER(PARTITION BY T1.키값)) AS 배분_소수점
,ROUND(T1.수량 * (T2.AMT / SUM(T2.AMT) OVER(PARTITION BY T1.키값)),0) AS 배분
FROM 테이블 T1
,임시테이블 T2
)
SELECT 키값, RN, 수량
, 배분_소수점
, 배분 
, 배분 + CASE WHEN RN = 1 THEN 수량 - SUM(배분) OVER(PARTITION BY 키값) ELSE 0 END  AS  결과값
FROM TEMP 
ORDER BY 키값, RN

대략 이런 식으로 처리하면 될듯 합니다.

제가 정확하게 이해한 거라면... 흠....

WITH t1 AS
(
-- Case 1 --
SELECT 1 no, 4 amt
UNION ALL SELECT 2, 2
-- Case 2 --
--SELECT 1 no, 2 amt
--UNION ALL SELECT 2, 2
--UNION ALL SELECT 3, 2
)
, t2 AS
(
SELECT 1 id, 2521 cnt
UNION ALL SELECT 2, 2220
)
SELECT a.id
     , a.cnt
     , b.no
     , b.amt
     , a.cnt * amt / s
     + CASE WHEN a.id = 1
       THEN a.cnt - SUM(a.cnt * amt / s) OVER(PARTITION BY a.id)
       ELSE 0
        END x
  FROM t2 a
 CROSS JOIN (SELECT no, amt, SUM(amt) OVER() s FROM t1) b
 ORDER BY a.id, b.no
;