例子:计算 ISO 周的标量值用户定义函数
下例中,用户定义函数 ISOweek 取日期参数并计算 ISO 周数。为了正确计算该函数,必须在调用该函数前唤醒调用 SET DATEFIRST 1。 CREATE FUNCTION ISOweek (@DATE datetime)
RETURNS int
AS
BEGIN
DECLARE @ISOweek int
SET @ISOweek= DATEPART(wk,@DATE)+1
-DATEPART(wk,CAST(DATEPART(yy,@DATE) as CHAR(4))+'0104')
--Special cases: Jan 1-3 may belong to the previous year
IF (@ISOweek=0)
SET @ISOweek=dbo.ISOweek(CAST(DATEPART(yy,@DATE)-1
AS CHAR(4))+'12'+ CAST(24+DATEPART(DAY,@DATE) AS CHAR(2)))+1
--Special case: Dec 29-31 may belong to the next year
IF ((DATEPART(mm,@DATE)=12) AND
((DATEPART(dd,@DATE)-DATEPART(dw,@DATE))>= 28))
SET @ISOweek=1
RETURN(@ISOweek)
END下面是函数调用。注意 DATEFIRST 设置为 1。SET DATEFIRST 1
SELECT master.dbo.ISOweek('12/26/1999') AS 'ISO Week'
下面是结果集。ISO Week
----------------
52
下例中,用户定义函数 ISOweek 取日期参数并计算 ISO 周数。为了正确计算该函数,必须在调用该函数前唤醒调用 SET DATEFIRST 1。 CREATE FUNCTION ISOweek (@DATE datetime)
RETURNS int
AS
BEGIN
DECLARE @ISOweek int
SET @ISOweek= DATEPART(wk,@DATE)+1
-DATEPART(wk,CAST(DATEPART(yy,@DATE) as CHAR(4))+'0104')
--Special cases: Jan 1-3 may belong to the previous year
IF (@ISOweek=0)
SET @ISOweek=dbo.ISOweek(CAST(DATEPART(yy,@DATE)-1
AS CHAR(4))+'12'+ CAST(24+DATEPART(DAY,@DATE) AS CHAR(2)))+1
--Special case: Dec 29-31 may belong to the next year
IF ((DATEPART(mm,@DATE)=12) AND
((DATEPART(dd,@DATE)-DATEPART(dw,@DATE))>= 28))
SET @ISOweek=1
RETURN(@ISOweek)
END下面是函数调用。注意 DATEFIRST 设置为 1。SET DATEFIRST 1
SELECT master.dbo.ISOweek('12/26/1999') AS 'ISO Week'
下面是结果集。ISO Week
----------------
52
create function f_a(@a int)
returns int
as
begin
return(@a+1)
end
go--调用
select dbo.f_a(100)
create function f_b(@name sysname)
returns table
as
return(select * from sysobjects where name=@name)
go--调用
select * from f_b('sysobjects')
create function f_a(@a int)
returns int
as
begin
return(@a+1)
end
go会出现如下的错误:
服务器: 消息 170,级别 15,状态 1,行 1
Line 1: Incorrect syntax near 'function'.
服务器: 消息 137,级别 15,状态 1,行 5
Must declare the variable '@a'.不知道该如何解决,请赐教!谢谢!