Tsql 如何在t-sql中计算一年中的iso周数?
我需要一个简单的查询来计算任何给定年份的iso周数?我认为这应该可以解决问题Tsql 如何在t-sql中计算一年中的iso周数?,tsql,iso,Tsql,Iso,我需要一个简单的查询来计算任何给定年份的iso周数?我认为这应该可以解决问题 DECLARE @year smallint = 2015; SELECT TheYear = @year, ISOWeeks= MAX(DATEPART(ISOWK,DATEADD(DD,N,CAST(CAST(@year AS char(4))+'1223' AS date)))) FROM (VALUES (1),(2),(3),(4),(5),(6),(7),(8)) t(N); 您可以在如下函数
DECLARE @year smallint = 2015;
SELECT
TheYear = @year,
ISOWeeks= MAX(DATEPART(ISOWK,DATEADD(DD,N,CAST(CAST(@year AS char(4))+'1223' AS date))))
FROM (VALUES (1),(2),(3),(4),(5),(6),(7),(8)) t(N);
您可以在如下函数中包含此逻辑:
CREATE FUNCTION dbo.CalculateISOWeeks(@year smallint)
RETURNS TABLE WITH SCHEMABINDING AS RETURN
SELECT ISOWeeks =
MAX(DATEPART(ISOWK,DATEADD(DD,N,CAST(CAST(@year AS char(4))+'1223' AS date))))
FROM (VALUES (1),(2),(3),(4),(5),(6),(7),(8)) t(N);
然后像这样使用它:
SELECT ISOWeeks FROM dbo.CalculateISOWeeks(2014);
SELECT
Yr = ISNULL(CAST(Yr AS smallint),0),
ISOWeeks = ISNULL(CAST(ISOWeeks AS tinyint),0)
INTO dbo.ISOCounts
FROM
(
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL))+1949
FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) a(x),
(VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) b(x)
) Years(Yr)
CROSS APPLY dbo.CalculateISOWeeks(Yr+1950);
CREATE UNIQUE CLUSTERED INDEX uci_ISOCounts ON dbo.ISOCounts(Yr);
或者更好的是。。。因为我们在计算一个静态值,为什么不把这些值放到一个表中,然后像这样索引它:
SELECT ISOWeeks FROM dbo.CalculateISOWeeks(2014);
SELECT
Yr = ISNULL(CAST(Yr AS smallint),0),
ISOWeeks = ISNULL(CAST(ISOWeeks AS tinyint),0)
INTO dbo.ISOCounts
FROM
(
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL))+1949
FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) a(x),
(VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) b(x)
) Years(Yr)
CROSS APPLY dbo.CalculateISOWeeks(Yr+1950);
CREATE UNIQUE CLUSTERED INDEX uci_ISOCounts ON dbo.ISOCounts(Yr);
现在,无论何时需要计算给定年份的ISO周数,都可以通过索引搜索从表中检索预先计算的值
SELECT * FROM dbo.ISOCounts WHERE yr = 2014;
结果:
Yr ISOWeeks
------ --------
2014 53