Sql server 如何在sql中对循环中的函数求和？

我们有一个函数，它接收4个变量并返回一个int结果。 我们希望对表中的每条记录使用此函数，而这4个变量取自每条记录

我该如何解决它

我的职能：

CREATE FUNCTION dbo.occupiedDaysPerListingFunction(@CheckIn date, @CheckOut date, @Email varchar(80), @Title varchar(50))
            RETURNS int
    AS
    BEGIN
    DECLARE @nightsInRange int  
    select @nightsInRange= (CASE  
    WHEN  DATEDIFF(day,@CheckIn,getdate()) >0 and DATEDIFF(day,@CheckOut,getdate())+100 <0 THEN 100
    WHEN  DATEDIFF(day,@CheckIn,getdate()) >0 and DATEDIFF(day,@CheckOut,getdate())+100 >0 THEN DATEDIFF(day,getdate(),@CheckOut)
    WHEN  DATEDIFF(day,getdate(),@CheckIn) >0 and DATEDIFF(day,getdate(),@CheckIn) <100 and DATEDIFF(day,@CheckOut,getdate())+100 >0 THEN DATEDIFF(day,@CheckIn,@CheckOut)
    WHEN  DATEDIFF(day,getdate(),@CheckIn) >0 and DATEDIFF(day,getdate(),@CheckIn) <100 and DATEDIFF(day,@CheckOut,getdate())+100 <0 THEN DATEDIFF(day,@CheckIn,getdate())+100
    WHEN  DATEDIFF(day,@CheckIn,getdate()) <0 THEN 0
END)
FROM [dbo].[ORDERS] o
        WHERE o.[E-mail] = @Email and o.[title]=@Title
        RETURN @nightsInRange
end

创建函数dbo.occupiedDaysPerListingFunction（@CheckIn-date、@CheckOut-date、@Email-varchar（80）、@Title-varchar（50））
返回整数
作为
开始
声明@nightsInRange int
选择@nightsInRange=（大小写）
当DATEDIFF（day，@CheckIn，getdate（））>0和DATEDIFF（day，@CheckOut，getdate（））+100 0和DATEDIFF（day，@CheckOut，getdate（））+100>0时，则为DATEDIFF（day，getdate（），@CheckOut）
当DATEDIFF（day，getdate（），@CheckIn）>0且DATEDIFF（day，getdate（），@CheckIn）为0时，则为DATEDIFF（day，@CheckIn，@CheckOut）
当DATEDIFF（day，getdate（），@CheckIn）>0和DATEDIFF（day，getdate（），@CheckIn）光标仅适用于此任务时。Сursor是可能的选项之一。您还可以使用WHILE循环、CTE等

DECLARE @iterator CURSOR
DECLARE @bufferTable TABLE 
(
    CheckIn date,
    CheckOut date,
    Email varchar(80),
    Title varchar(50)
)

SET @iterator = CURSOR FOR
SELECT
    CheckIn,
    CheckOut,
    Email,
    Title
FROM  [YourDatabase].[YourSchema].[YourTable]    

OPEN @iterator 

FETCH NEXT FROM @iterator 
INTO @bufferTable

WHILE @@FETCH_STATUS = 0
BEGIN

    /* Your function comes into play */
    dbo.occupiedDaysPerListingFunction(@bufferTable.CheckIn, @bufferTable.CheckOut, @bufferTable.Email, @bufferTable.Title)

    FETCH NEXT FROM @iterator 
    INTO @bufferTable 
END; 

CLOSE @iterator
DEALLOCATE @iterator

GO

编辑：

根据@的回答，您可以缩小SELECT查询的范围，如下所示：

SELECT InnerQueryTable.OccupiedDaysPerListing FROM 
(
    SELECT
        CheckInDate,
        CheckOutDate,
        Email,
        Title,
        dbo.occupiedDaysPerListingFunction(CheckInDate, CheckOutDate, Email, Title) AS OccupiedDaysPerListing
    FROM
        [YourDatabase].[YourSchema].[YourTable]
) AS InnerQueryTable
GO

CREATE FUNCTION dbo.occupiedDaysPerListingFunction(@CheckIn DATE, @CheckOut 
DATE, @Email VARCHAR(80), @Title VARCHAR(50))
RETURNS INT
AS
BEGIN
    DECLARE @nightsInRange INT = 0;
    SET @nightsInRange = (SELECT TOP 1 CASE  
        WHEN  DATEDIFF(day,@CheckIn,getdate()) >0 and     DATEDIFF(day,@CheckOut,getdate())+100 <0 THEN 100
        WHEN  DATEDIFF(day,@CheckIn,getdate()) >0 and     DATEDIFF(day,@CheckOut,getdate())+100 >0 THEN DATEDIFF(day,getdate(),@CheckOut)
        WHEN  DATEDIFF(day,getdate(),@CheckIn) >0 and     DATEDIFF(day,getdate(),@CheckIn) <100 and DATEDIFF(day,@CheckOut,getdate())+100     >0 THEN DATEDIFF(day,@CheckIn,@CheckOut)
        WHEN  DATEDIFF(day,getdate(),@CheckIn) >0 and     DATEDIFF(day,getdate(),@CheckIn) <100 and DATEDIFF(day,@CheckOut,getdate())+100     <0 THEN DATEDIFF(day,@CheckIn,getdate())+100
        WHEN  DATEDIFF(day,@CheckIn,getdate()) <0 THEN 0
        ELSE 0
    END
    FROM [dbo].[ORDERS] o
    WHERE o.[E-mail] = @Email and o.[title]=@Title)

    RETURN @nightsInRange
END

SELECT
    CheckInDate,
    CheckOutDate,
    Email,
    Title,
    dbo.occupiedDaysPerListingFunction(CheckInDate, CheckOutDate, Email,     Title) AS OccupiedDaysPerListing
FROM
    [YourDatabase].[YourSchema].[YourTable]

<>我将开始确保你的函数总是返回一个整数。你当前的函数用电子邮件和标题的一个过滤器向你的[订单]表发送一个查询。你应该考虑如果你的[订单]表包含多个具有相同电子邮件和标题的行，将会发生什么。

首先，我将重写函数，如下所示：

SELECT InnerQueryTable.OccupiedDaysPerListing FROM 
(
    SELECT
        CheckInDate,
        CheckOutDate,
        Email,
        Title,
        dbo.occupiedDaysPerListingFunction(CheckInDate, CheckOutDate, Email, Title) AS OccupiedDaysPerListing
    FROM
        [YourDatabase].[YourSchema].[YourTable]
) AS InnerQueryTable
GO

CREATE FUNCTION dbo.occupiedDaysPerListingFunction(@CheckIn DATE, @CheckOut 
DATE, @Email VARCHAR(80), @Title VARCHAR(50))
RETURNS INT
AS
BEGIN
    DECLARE @nightsInRange INT = 0;
    SET @nightsInRange = (SELECT TOP 1 CASE  
        WHEN  DATEDIFF(day,@CheckIn,getdate()) >0 and     DATEDIFF(day,@CheckOut,getdate())+100 <0 THEN 100
        WHEN  DATEDIFF(day,@CheckIn,getdate()) >0 and     DATEDIFF(day,@CheckOut,getdate())+100 >0 THEN DATEDIFF(day,getdate(),@CheckOut)
        WHEN  DATEDIFF(day,getdate(),@CheckIn) >0 and     DATEDIFF(day,getdate(),@CheckIn) <100 and DATEDIFF(day,@CheckOut,getdate())+100     >0 THEN DATEDIFF(day,@CheckIn,@CheckOut)
        WHEN  DATEDIFF(day,getdate(),@CheckIn) >0 and     DATEDIFF(day,getdate(),@CheckIn) <100 and DATEDIFF(day,@CheckOut,getdate())+100     <0 THEN DATEDIFF(day,@CheckIn,getdate())+100
        WHEN  DATEDIFF(day,@CheckIn,getdate()) <0 THEN 0
        ELSE 0
    END
    FROM [dbo].[ORDERS] o
    WHERE o.[E-mail] = @Email and o.[title]=@Title)

    RETURN @nightsInRange
END

SELECT
    CheckInDate,
    CheckOutDate,
    Email,
    Title,
    dbo.occupiedDaysPerListingFunction(CheckInDate, CheckOutDate, Email,     Title) AS OccupiedDaysPerListing
FROM
    [YourDatabase].[YourSchema].[YourTable]

希望这能有所帮助。
问题的标题提到了“sum”，但这并没有出现在问题中。为什么不呢？一般来说，
TOP
应该与
ORDER BY
配对。在这种情况下，任何行都可以，值得添加一条注释来解释预期的行为。请注意，
GetDate（）的每个实例
将为所有行返回单个值，但不同的实例可能返回不同的值。最佳做法是获取单个值，例如
将@Now声明为DateTime=GetDate（）；
，并在函数的其余部分使用变量
@Now
。同意您的观点，@HABO。这将是查询的额外改进。在这种情况下，他很可能希望按OrderDate降序。即
按[OrderDate]DESC下单