[英]Dividing values in a GROUP BY query
I am trying to divide numHospitalizations by numCases to get percent hospitalized and numDeaths by numCases to get percent death.我试图将 numHospitalizations 除以 numCases 以获得住院百分比,并将 numDeaths 除以 numCases 以获得死亡百分比。 There is a lot of repeat health districts so I thought it would be best to group by healthDistrict but I keep getting:
有很多重复的健康区,所以我认为最好按健康区分组,但我不断得到:
not a GROUP BY expression.
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);
I'm guessing this is what you're after, but an MCVE would be really useful .我猜这就是您所追求的,但是MCVE 会非常有用。
;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;
You need to form aggregates of all columns that you are not grouping on (and prevent division by zero).您需要形成所有未分组的列的聚合(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);
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