根据一个人的出生日期和今天的日期，计算他最近的生日（使用Northwind数据库的Employees表）

使用Northwind的Employees表，根据存储的Birthdate返回每个员工离今天最近的生日，如果今年的生日已经过了，则返回明年的，反之，则返回今年的（注意，如果是闰年2月29日出生的，则在下个月的3月1号过生日）

WITH    arg1


[code]AS ( SELECT   FirstName ,

LastName ,

BirthDate ,

DATEDIFF(YEAR, BirthDate, GETDATE()) AS DIFF ,

CAST(CONVERT(CHAR(8), GETDATE(), 112) AS DATETIME) AS Today

FROM     Employees

),

arg2

AS ( SELECT   FirstName ,

LastName ,

BirthDate ,

DATEADD(YEAR, DIFF, BirthDate) AS CurrentBirthday ,

DATEADD(YEAR, DIFF + 1, BirthDate) AS NextBirthday ,

Today

FROM     arg1

),

arg3

AS ( SELECT   FirstName ,

LastName ,

BirthDate ,

CurrentBirthday

+ CASE WHEN DAY(BirthDate) = 29

AND DAY(CurrentBirthday) = 28 THEN 1

ELSE 0

END AS CurrentBirthday ,

NextBirthday

+ CASE WHEN DAY(Birthdate) = 29

AND DAY(NextBirthday) = 28 THEN 1

ELSE 0

END AS NextBirthday ,

Today

FROM     arg2

)

SELECT  FirstName ,

LastName ,

BirthDate ,

CASE WHEN Today > CurrentBirthday THEN NextBirthday

ELSE CurrentBirthday

END AS Birthday

FROM    arg3

[/code]

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