今天查看以前專案的數(shù)據(jù)庫自定義函數(shù),溫習(xí)溫習(xí)。發(fā)現(xiàn)其中有一個函數(shù),是獲取月份的天數(shù)的自定義函數(shù)。
如下:
代碼如下:
CREATE FUNCTION [dbo].[udf_DaysInMonth]
(
@Date DATETIME
)
RETURNS INT
AS
BEGIN
DECLARE @dim AS TABLE (M INT,Dy INT)
INSERT INTO @dim VALUES
(1,31),(3,31),(5,31),(7,31),(8,31),(10,31),(12,31),
(4,30),(6,30),(9,30),(11,30),
(2,
CASE WHEN (YEAR(@Date) % 4 = 0 AND YEAR(@Date) % 100 0) OR (YEAR(@Date) % 400 = 0)
THEN 29
ELSE 28 END
)
DECLARE @RValue INT
SELECT @RValue = [Dy] FROM @dim WHERE [M] = MONTH(@Date)
RETURN @RValue
END
GO
獲取月份天數(shù),以前在博客上也有寫過,不過它只是取得二月份的天數(shù)。鏈接如下:http://www.cnblogs.com/insus/articles/2025019.html
現(xiàn)第一眼看見專案中這個函數(shù),總覺它寫得不夠好的感覺,是否能把它改寫得更好些,啟發(fā)點也是從獲取二月份天數(shù)的CASE函數(shù)想起的。
因此,我嘗試改了,如下:
代碼如下:
CREATE FUNCTION [dbo].[udf_DaysInMonth]
(
@Date DATETIME
)
RETURNS INT
AS
BEGIN
RETURN CASE WHEN MONTH(@Date) IN (1,3,5,7,8,10,12) THEN 31
WHEN MONTH(@Date) IN (4,6,9,11) THEN 30
ELSE CASE WHEN (YEAR(@Date) % 4 = 0 AND YEAR(@Date) % 100 0) OR (YEAR(@Date) % 400 = 0)
THEN 29
ELSE 28
END
END
END
如果你已經(jīng)有引過Insus.NET那個獲取二月份天數(shù)的自定義函數(shù),也可以參考下面這個版本:
代碼如下:
CREATE FUNCTION [dbo].[udf_DaysInMonth]
(
@Date DATETIME
)
RETURNS INT
AS
BEGIN
RETURN CASE WHEN MONTH(@Date) IN (1,3,5,7,8,10,12) THEN 31
WHEN MONTH(@Date) IN (4,6,9,11) THEN 30
ELSE [dbo].[DaysOfFebruary](YEAR(@Date))
END
END