計數基於年齡SQL

Question

我有以下的T-SQL來計算年齡：

SELECT 
    Member_ID, 
    DATEDIFF(YY,DOB,GETDATE()) - 
    CASE 
    WHEN DATEADD(YY,DATEDIFF(YY,DOB,GETDATE()),DOB) > GETDATE() THEN 1 
    ELSE 0 
    END AS Age in Years 
FROM MEMBER 
WHERE YEAR(registration_date) >= 2012 

如何計算成員ID的每個年齡段的年數？

Answer 1

事情是這樣的：

SELECT 
-- Member_ID, commented out 
DATEDIFF(YY,DOB,GETDATE()) - 
CASE 
WHEN DATEADD(YY,DATEDIFF(YY,DOB,GETDATE()),DOB) > GETDATE() THEN 1 
ELSE 0 
END AS Age in Years 
, count(member_id) membersWithThisAge 
FROM MEMBER 
WHERE YEAR(registration_date) >= 2012 
group by DATEDIFF(YY,DOB,GETDATE()) - 
CASE 
WHEN DATEADD(YY,DATEDIFF(YY,DOB,GETDATE()),DOB) > GETDATE() THEN 1 
ELSE 0 
END 

的member_id不能包括選擇子句。如果是這樣，那麼你會得到每個成員一個年齡的計數。

Answer 2

我會這樣做使用子查詢或CTE。更容易遵循：

SELECT AgeInYears, COUNT(*) 
FROM (SELECT Member_ID, 
      (DATEDIFF(YY,DOB,GETDATE()) - 
       CASE WHEN DATEADD(YY,DATEDIFF(YY,DOB,GETDATE()),DOB) > GETDATE() THEN 1 
        ELSE 0 
       END) AS AgeinYears 
     FROM MEMBER 
     WHERE YEAR(registration_date) >= 2012 
    ) m 
GROUP BY AgeInYears 
ORDER BY 1;