在 GROUP BY 查询中除以值

Question

我试图将 numHospitalizations 除以 numCases 以获得住院百分比，将 numDeaths 除以 numCases 以获得死亡百分比。有很多重复的卫生区，所以我认为最好按 healthDistrict 分组，但我不断得到：

不是 GROUP BY 表达式。

SELECT healthDistrict AS HEALTH_DISTRICT
    , (numHospitalizations / numCases) AS PERCENTHOSP
    , (numDeaths / numCases) AS PERCENTDEATH
FROM CovidReport
GROUP BY UPPER(healthDistrict);

Answer 1

您需要对未分组的所有列进行聚合（并防止被零除）。

SELECT
  UPPER(healthDistrict) AS HEALTH_DISTRICT,
  CASE WHEN SUM(numCases) > 0 THEN SUM(numHospitalizations) * 1.0 / SUM(numCases) ELSE 0 END AS PERCENTHOSP,
  CASE WHEN SUM(numCases) > 0 THEN SUM(numDeaths) * 1.0 / SUM(numCases) ELSE 0 END AS PERCENTDEATH
FROM
  SomethingSlightlyLessMorbid
GROUP BY
  UPPER(healthDistrict);

Answer 2

我猜这就是你想要的，但an MCVE would be really useful。

;WITH agg AS
(
  SELECT 
    UPPER(healthDistrict) AS HEALTH_DISTRICT, 
    Hosp   = SUM(numHospitalizations)*1.0,
    Cases  = NULLIF(SUM(numCases)*1.0,0),
    Deaths = SUM(numDeaths)*1.0
  FROM dbo.SomethingSlightlyLessMorbid
  GROUP BY UPPER(healthDistrict)
)
SELECT HEALTH_DISTRICT,
       PERCENTHOSP  = CONVERT(decimal(8,2), (Hosp   / Cases)), 
       PERCENTDEATH = CONVERT(decimal(8,2), (Deaths / Cases))
FROM agg;

• 示例db<>fiddle