使用来自不同行的值的 CASE 表达式

Question

我有以下table

WITH TMP AS (
SELECT 'XX' AS AGG, 50 AS VALUE, 0 AS MONTH
UNION ALL
SELECT 'XX' AS AGG, 150 AS VALUE, 1 AS MONTH
UNION ALL
SELECT 'XX' AS AGG, 300 AS VALUE, 2 AS MONTH
UNION ALL
SELECT 'YY' AS AGG, 25 AS VALUE, 0 AS MONTH
UNION ALL
SELECT 'YY' AS AGG, 50 AS VALUE, 1 AS MONTH
UNION ALL
SELECT 'YY' AS AGG, 75 AS VALUE, 2 AS MONTH
UNION ALL
SELECT 'ZZ' AS AGG, 500 AS VALUE, 0 AS MONTH
UNION ALL
SELECT 'ZZ' AS AGG, 600 AS VALUE, 1 AS MONTH
UNION ALL
SELECT 'ZZ' AS AGG, 700 AS VALUE, 2 AS MONTH
)
-- CASE WHEN VALUE OF 'XX' > 0 THEN VALUE OF 'ZZ' ELSE 0 END
SELECT 
*
FROM TMP
WHERE 1 = 1

我需要始终考虑月份来应用以下业务逻辑。

CASE WHEN VALUE OF 'XX' > 0 THEN VALUE OF 'ZZ' ELSE 0 END

此逻辑应映射到新的 table。结果应该类似于下面的 table。
我想避免加入相同的 table。这是否可以使用 window 函数或类似的东西以某种方式实现？这个想法是在同一个 sql 语句中构建多个 case when 语句。

IE1	MONTH
500	00
600	01
700	02

Answer 1

透视（有条件地聚合）您的数据，然后 return 根据您的表达式需要的值：

WITH TMP AS
    (SELECT 'XX' AS AGG,
            50 AS VALUE,
            0 AS MONTH
     UNION ALL
     SELECT 'XX' AS AGG,
            150 AS VALUE,
            1 AS MONTH
     UNION ALL
     SELECT 'XX' AS AGG,
            300 AS VALUE,
            2 AS MONTH
     UNION ALL
     SELECT 'YY' AS AGG,
            25 AS VALUE,
            0 AS MONTH
     UNION ALL
     SELECT 'YY' AS AGG,
            50 AS VALUE,
            1 AS MONTH
     UNION ALL
     SELECT 'YY' AS AGG,
            75 AS VALUE,
            2 AS MONTH
     UNION ALL
     SELECT 'ZZ' AS AGG,
            500 AS VALUE,
            0 AS MONTH
     UNION ALL
     SELECT 'ZZ' AS AGG,
            600 AS VALUE,
            1 AS MONTH
     UNION ALL
     SELECT 'ZZ' AS AGG,
            700 AS VALUE,
            2 AS MONTH),
--Solution
/*WITH */Pvt AS(
    SELECT Month,
           MAX(CASE Agg WHEN 'XX' THEN VALUE END) AS XX,
           --MAX(CASE Agg WHEN 'YY' THEN VALUE END) AS YY,--Not needed hence commented out
           MAX(CASE Agg WHEN 'ZZ' THEN VALUE END) AS ZZ
    FROM TMP
    GROUP BY MONTH)
SELECT CASE WHEN XX > 0 THEN ZZ ELSE 0 END AS IE1,
       MONTH
FROM Pvt;

使用来自不同行的值的 CASE 表达式

CASE expressions using values from different rows

sql

sql-server

case