标量函数是非确定性的

Question

我想保留这个字段，但不知道为什么它是不确定的。

CREATE FUNCTION GetServiceMinutes
(
    -- Add the parameters for the function here
    @StartDate datetime,
    @EndDate datetime
)
RETURNS int WITH SCHEMABINDING
AS
BEGIN
    DECLARE @Result int

    SET @StartDate = CASE WHEN DATEPART(HOUR, @StartDate) < 8 THEN DATEADD(DAY, DATEDIFF(DAY, 0, @StartDate), '08:00:00')  ELSE @StartDate END
    SET @EndDate = CASE WHEN DATEPART(HOUR, @EndDate) >= 17 THEN DATEADD(DAY, DATEDIFF(DAY, 0, @EndDate), '17:00:00') ELSE @EndDate END
    
    SET @Result = 
         CASE WHEN DATEPART(DAY, @StartDate) != DATEPART(DAY, @EndDate) THEN 1000
              WHEN DATEPART(HOUR, @EndDate) < 8 THEN 0
              WHEN DATEPART(HOUR, @StartDate) >= 17 THEN 0
              ELSE DATEDIFF(MINUTE, @StartDate, @EndDate)
    END
    
    RETURN @Result

END
GO

这将返回 0

SELECT OBJECTPROPERTY(OBJECT_ID('[dbo].GetServiceMinutes'), 'IsDeterministic')

使用 SQL Server 2017

Answer 1

正如我所提到的，问题是您使用（日期和）时间值的隐式转换。根据documentation：

以下函数并不总是确定性的，但当它们以确定性方式指定时，可用于索引视图或计算列的索引。

Function	Comments
all aggregate functions	All aggregate functions are deterministic unless they are specified with the OVER and ORDER BY clauses. For a list of these functions, see Aggregate Functions (Transact-SQL).
CAST	Deterministic unless used with datetime, smalldatetime, or sql_variant.
CONVERT	Deterministic unless one of these conditions exists: Source type is sql_variant. Target type is sql_variant and its source type is nondeterministic. Source or target type is datetime or smalldatetime, the other source or target type is a character string, and a nondeterministic style is specified. To be deterministic, the style parameter must be a constant. Additionally, styles less than or equal to 100 are nondeterministic, except for styles 20 and 21. Styles greater than 100 are deterministic, except for styles 106, 107, 109 and 113.

在您的函数中，您有隐式转换，例如 '08:00:00' 到 datetime。你需要明确：

CREATE FUNCTION dbo.GetServiceMinutes
(
    -- Add the parameters for the function here
    @StartDate datetime,
    @EndDate datetime
)
RETURNS int WITH SCHEMABINDING
AS
BEGIN
    DECLARE @Result int

    SET @StartDate = CASE WHEN DATEPART(HOUR, @StartDate) < 8 THEN DATEADD(DAY, DATEDIFF(DAY, 0, @StartDate), CONVERT(datetime,'1900-01-01T08:00:00',126))  ELSE @StartDate END
    SET @EndDate = CASE WHEN DATEPART(HOUR, @EndDate) >= 17 THEN DATEADD(DAY, DATEDIFF(DAY, 0, @EndDate), CONVERT(datetime,'1900-01-01T17:00:00',126)) ELSE @EndDate END
    
    SET @Result = 
         CASE WHEN DATEPART(DAY, @StartDate) != DATEPART(DAY, @EndDate) THEN 1000
              WHEN DATEPART(HOUR, @EndDate) < 8 THEN 0
              WHEN DATEPART(HOUR, @StartDate) >= 17 THEN 0
              ELSE DATEDIFF(MINUTE, @StartDate, @EndDate)
    END
    
    RETURN @Result

END
GO

SELECT OBJECTPROPERTY(OBJECT_ID('[dbo].GetServiceMinutes'), 'IsDeterministic')