在case語句中使用標量函數

我有一個用戶定義的標量函數，名爲fn_CountWeekDays，它接受2個參數startdate和enddate並返回一個整數值。該功能基本上計算開始和結束日期之間的平日的no。在case語句中使用標量函數

功能代碼：

CREATE FUNCTION [dbo].[fn_CountWeekDays] 
(
    @fromdate Datetime, 
    @todate Datetime 

) 
RETURNS INT AS 

Begin 
Declare @NoOfWeekDays int 
Set @NoOfWeekDays = (DATEDIFF(dd, @fromdate, @todate) + 1) 
    -(DATEDIFF(wk, @fromdate, @todate) * 2) 
    -(CASE WHEN DATENAME(dw, @fromdate) = 'Sunday' THEN 1 ELSE 0 END) 
    -(CASE WHEN DATENAME(dw, @todate) = 'Saturday' THEN 1 ELSE 0 END) 

    Return @NoOfWeekDays 
End

如何調用該函數在一個case語句，並將其與其他整數值在同一時間比較？

下面是我的查詢：

select 
Case 
    when Priority in ('1 - Critical','2 - High') and fn_CountWeekDays(Opened,Closed) <= 3 and ProblemState = 'Closed/Resolved' then 1 else 0 
End as RCA_KPI_P1_P2_Met, 
Case 
    when Priority = '3 - Moderate' and fn_CountWeekDays(Opened,Closed) <= 5 and ProblemState = 'Closed/Resolved' then 1 else 0 
End as RCA_KPI_P3_Met 

from v_Problem

來源

2017-05-31 Rajiv Iyer

這不起作用？它看起來應該是 – nimdil

我希望這也可以工作。從性能角度來看，將函數重寫爲表值函數會更好 – HoneyBadger

如何使用表值函數？我已更新該帖子以包含功能代碼。 –

是您的功能內嵌表值函數，而不是一個標量函數？如果是這樣，那麼你可能需要使用它的子查詢或cross apply()像這樣：

select 
    case 
    when Priority in ('1 - Critical', '2 - High') 
     and w.WeekDays <= 3 
     and ProblemState = 'Closed/Resolved' 
     then 1 
    else 0 
    end as RCA_KPI_P1_P2_Met 
    , case 
    when Priority = '3 - Moderate' 
     and w.WeekDays <= 5 
     and ProblemState = 'Closed/Resolved' 
     then 1 
    else 0 
    end as RCA_KPI_P3_Met 
from v_Problem 
    cross apply tvf_CountWeekDays(Opened,Closed) w

如果你的函數不是內嵌表值函數，那麼你或許應該寫一個是像這樣：

create function [dbo].[tvf_CountWeekDays] (@fromdate datetime,@todate datetime) 
returns table with schemabinding as return (
    select 
     WeekDays = (datediff(day, @fromdate, @todate) + 1) 
     - (datediff(week, @fromdate, @todate) * 2) 
     - (case when datename(weekday, @fromdate) = 'Sunday' then 1 else 0 end) 
     - (case when datename(weekday, @todate) = 'Saturday' then 1 else 0 end) 
) 
go

參考：

來源

2017-05-31 13:22:18 SqlZim

我的函數是標量值。我應該使用您建議的查詢嗎？ –

在case語句中使用標量函數

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