将多个 SUM(CASE) 添加到同一列

Question

我在 DB2 中有下表：

COLUMN_NAME	DATA_TYPE	TYPE_NAME	COLUMN_SIZE	COLUMN_TEXT
DMYEAR	3	DECIMAL	4	Fiscal Year
DMYTYP	-2	CHAR () FOR BIT DATA	1	Year Type
DMPTYP	-2	CHAR () FOR BIT DATA	1	Period Type
DMTYPE	-2	CHAR () FOR BIT DATA	6	Type of Data
DMPROD	-2	CHAR () FOR BIT DATA	35	Product Code
DMVL01	3	DECIMAL	17	Value Period 1
DMVL02	3	DECIMAL	17	Value Period 2
DMVL03	3	DECIMAL	17	Value Period 3
DMVL04	3	DECIMAL	17	Value Period 4
DMVL05	3	DECIMAL	17	Value Period 5
DMVL06	3	DECIMAL	17	Value Period 6
DMVL07	3	DECIMAL	17	Value Period 7
DMVL08	3	DECIMAL	17	Value Period 8
DMVL09	3	DECIMAL	17	Value Period 9
DMVL10	3	DECIMAL	17	Value Period 10
DMVL11	3	DECIMAL	17	Value Period 11
DMVL12	3	DECIMAL	17	Value Period 12

数值周期为1-2月，可以总结每个月的各种数据类型，如下所示：

SELECT 
DMYEAR,
DMPTYP,
DMPROD,
Sum(CASE WHEN DMTYPE = 'COST' THEN DMVL01 ELSE 0 END) AS COST,
Sum(CASE WHEN DMTYPE = 'COST' THEN DMVL02 ELSE 0 END) AS COST,
Sum(CASE WHEN DMTYPE = 'COST' THEN DMVL03 ELSE 0 END) AS COST,
Sum(CASE WHEN DMTYPE = 'RTNCST' THEN DMVL01 ELSE 0 END) AS RTNCST,
Sum(CASE WHEN DMTYPE = 'RTNCST' THEN DMVL02 ELSE 0 END) AS RTNCST,
Sum(CASE WHEN DMTYPE = 'RTNCST' THEN DMVL03 ELSE 0 END) AS RTNCST
FROM DWM
WHERE DMPTYP = 'M' 
GROUP BY DMYEAR, DMPTYP, DMPROD
ORDER BY 1, 3

产生这样的输出：

DMYEAR	DMPTYP	DMPROD	COST	COST	COST	RTNCST	RTNCST	RTNCST
2010	M	11105	435798.00000	441252.00000	479774.00000	-2921.00000	0.00000	0.00000
2010	M	11350	538938.00000	593764.00000	511088.00000	-4074.00000	-2503.00000	0.00000
2010	M	11364	2905557.00000	3167448.00000	3534924.00000	-5691.00000	0.00000	0.00000
2010	M	11374	854274.00000	829392.00000

但我想为月份创建一个新列，表示 1-12 并调整总和以产生相应的值，使其看起来像这样：

DMYEAR	DMMONTH	DMPTYP	DMPROD	COST	RTNCST
2011	1	M	11105	278021.00000	-7522.00000
2011	2	M	11105	615232.00000	-938.00000
2011	3	M	11105	2153272.00000	-2805.00000

我认为子查询是可能的，但请记住，我有 8-9 种不同的 DMTYPE，所以我希望有一个比为每个 DMTYPE 制作 9 个 case 语句更优雅的解决方案。

Answer 1

尝试将相应的表达式添加到内部 CASE 以获得所有 12 个 (x, DMVLx) 对：

WITH 
  T (DMMONTH) AS (VALUES 1 UNION ALL SELECT DMMONTH + 1 FROM T WHERE DMMONTH < 12)
SELECT 
  DMYEAR, DMMONTH, DMPTYP, DMPROD
, Sum (CASE WHEN DMTYPE = 'COST'   THEN CASE DMMONTH WHEN 1 THEN DMVL01 WHEN 2 THEN DMVL02 ... WHEN 12 THEN DMVL12 END ELSE 0 END) AS COST
, Sum (CASE WHEN DMTYPE = 'RTNCST' THEN CASE DMMONTH WHEN 1 THEN DMVL01 WHEN 2 THEN DMVL02 ... WHEN 12 THEN DMVL12 END ELSE 0 END) AS RTNCST
FROM DWM, T
WHERE DMPTYP = 'M' 
GROUP BY DMYEAR, DMMONTH, DMPTYP, DMPROD
ORDER BY 1, 3