tsql - 如何使用 select 语句设置变量并在 case 语句中使用它

Question

我正在使用案例语句来确定几个不同年龄组的 Count(*)，但我需要获取每个年龄组的百分比，因为它与所有年龄组的总数有关。我知道这是一个新手问题，但我被卡住了。谢谢安迪

这是我尝试使用的代码。

WITH AgeGroups AS ( 
SELECT 
CASE 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) < 21 THEN 'Under   21' 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) BETWEEN 21 AND 29 THEN '21 - 29' 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) BETWEEN 30 AND 39 THEN '30 - 39' 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) BETWEEN 40 AND 49 THEN '40 - 49'
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) BETWEEN 50 AND 59 THEN '50 - 59' 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) > 60 THEN '60 and Over' 
ELSE 'Unkown' 
END AS AgeGroup  
FROM party   
LEFT OUTER JOIN volunteer on partyID = volunteer.partyID 
WHERE volunteer.swornDate BETWEEN @startDate AND @endDate) 
SELECT  AgeGroup, COUNT(*) AS AgeGroupCount, Convert(decimal(18,2),  
(1.0*Count(*)/@Total * 100)) as percentage 

FROM AgeGroups 
GROUP BY AgeGroup

我正在尝试用所有年龄组的计数填充变量 @Total

Answer 1

从您的问题中，不清楚您是要填写 @Total 还是生成查询输出。

如果是后者，那么这可能对您有用。

WITH AgeGroups AS ( 
SELECT 
CASE 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) < 21 THEN 'Under   21' 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) BETWEEN 21 AND 29 THEN '21 - 29' 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) BETWEEN 30 AND 39 THEN '30 - 39' 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) BETWEEN 40 AND 49 THEN '40 - 49'
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) BETWEEN 50 AND 59 THEN '50 - 59' 
WHEN DATEDIFF(YEAR, party.birthdate, GETDATE()) > 60 THEN '60 and Over' 
ELSE 'Unkown' 
END AS AgeGroup,
FROM party   
LEFT OUTER JOIN volunteer on partyID = volunteer.partyID 
WHERE volunteer.swornDate BETWEEN @startDate AND @endDate
) 
SELECT  AgeGroup,COUNT(*) AS AgeGroupCount,  Convert(decimal(18,2),  
(1.0*Count(*)/b.totcnt * 100)) as percentage 

FROM AgeGroups a,
(select COUNT(*) AS totcnt from AgeGroups) b

GROUP BY a.AgeGroup