年がうるう年の場合の機能チェックの作成

この単純な関数は渡された年をチェックし、1行のコードで年に応じてtrueまたはfalseを返します

This simple little function is normally called by other database operation calculating age and year differences.

When you run DATEPART DAYOFYEAR and compare the number of days on 3rd March then a leap year will return one more day, which is correct, but needs to be coded around for calculating someones age.

To get around this, we append this function to one of the dates to subtract one day after February 29.

CREATE FUNCTION Dates.GetLeapYear(@Date DATETIME2) RETURNS BIT AS BEGINDECLARE @Ret BIT=(CASE WHEN DATEPART(YEAR,@Date)%4<>0 OR (DATEPART(YEAR,@Date)%100=0 AND DATEPART(YEAR,@Date)%400<>0) THEN 0 ELSE 1 END)RETURN @RetENDGO

SELECT  [dbo].[GetLeapYear]('01-01-1900') [1900],[dbo].[GetLeapYear]('01-01-1901') [1901],[dbo].[GetLeapYear]('01-01-1902') [1902],[dbo].[GetLeapYear]('01-01-1903') [1903],[dbo].[GetLeapYear]('01-01-1904') [1904]

Only 1904 will return true as expected.