檢查閏年

Question

如何檢查是否一年是閏年？

我有這樣的代碼：

declare @year int 
set @year = 1968 

SELECT CASE WHEN @YEAR = <LEAPYEAR> THEN 'LEAP YEAR' ELSE 'NORMAL YEAR' END 

預期結果：

LEAP YEAR 

Answer 1

檢查二月二十九日：

CASE WHEN ISDATE(CAST(@YEAR AS char(4)) + '0229') = 1 THEN 'LEAP YEAR' ELSE 'NORMAL YEAR' END 

，或者使用下面的規則

CASE WHEN (@YEAR % 4 = 0 AND @YEAR % 100 <> 0) OR @YEAR % 400 = 0 THEN 'LEAP YEAR'... 

Answer 2

閏年的計算：

(@year % 4 = 0) and (@year % 100 != 0) or (@year % 400 = 0) 

如果這是真的，那麼它是一個閏年。或者把它放在case語句

select case when 
    (
     (@year % 4 = 0) and (@year % 100 != 0) or 
     (@year % 400 = 0) 
    ) then 'LEAP' else 'USUAL' end 
; 

Answer 3

我有一個更好的解決方案

CREATE FUNCTION dbo.IsLeapYear(@year INT) 
RETURNS BIT AS 
    BEGIN 
      DECLARE @d DATETIME, 
        @ans BIT  
      SET @d = CONVERT(DATETIME,'31/01/'+CONVERT(VARCHAR(4),@year),103) 
      IF DATEPART(DAY,DATEADD(MONTH,1,@d))=29 SET @ans=1 ELSE SET @ans=0 
      RETURN @ans 
    END 
GO 

隨意使用

Answer 4

select 

CASE 

    WHEN result = 0 THEN 'Leap_Year' 

    WHEN result <> 0 THEN 'Not_A_Leap_Year' 

END 

from(select mod((EXTRACT(YEAR FROM DATE '2013-08-23')), 4) result FROM DUAL); 

Answer 5

select decode(mod(&n,4),0,'leap year' ,'not a leapyear') as CHECK_LEAPYEAR from dual 

Answer 6

這也可以幫助

DECLARE @year INT = 2012 

SELECT IIF(DAY(EOMONTH(DATEFROMPARTS(@year,2,1))) = 29,1,0) 
Result: 1 --(1 if Leap Year, 0 if not) 

SELECT IIF(DAY(EOMONTH(DATEFROMPARTS(@year,2,1))) = 29,'Leap year','Not Leap year') 
Result: Leap year