如何在表值函數中使用條件聯合ALL？

Question

以下是內聯表值函數

CREATE FUNCTION [dbo].[GetDipForDirectClientCharts] 
(
    @FacilityId AS UNIQUEIDENTIFIER , 
    @PatientChartStatusCompleteEnum SMALLINT , 
    @PatientChartLockingInterval SMALLINT 
) 
RETURNS TABLE 
AS RETURN 
(   
    WITH DirectPatientChartCTE 
       --Get all patient charts that qualify for dip criteria 
       AS (SELECT TOP 500 
          VisitNumber,PatientChartID 
        FROM  PatientChartCorporate WITH (READPAST) 
        WHERE PatientChartCorporate.IsDeleted = 0 
          AND PatientChartCorporate.IsErroneous = 0 
          AND PatientChartCorporate.FacilityId = @FacilityId 
          AND (DipFileName IS NULL 
            OR DipFileName = '' 
           ) 
          AND PatientChartCorporate.ChartStatusID = @PatientChartStatusCompleteEnum 
          AND DATEDIFF(MINUTE, CompletedOn, GETUTCDATE()) >= +CONVERT(VARCHAR(30), @PatientChartLockingInterval) 
          AND (PatientChartCorporate.CompletedOn IS NOT NULL) 
       ), 
      RemotePatientChartCTE 
       AS (SELECT TOP 500 
          VisitNumber,PatientChartID 
        FROM  PatientCharts WITH (READPAST) 
        WHERE PatientCharts.IsDeleted = 0 
          AND PatientCharts.IsErroneous = 0 
          AND PatientCharts.FacilityId = @FacilityId 
          AND (DipFileName IS NULL 
            OR DipFileName = '' 
           ) 
          AND PatientCharts.ChartStatusID = @PatientChartStatusCompleteEnum 
          AND DATEDIFF(MINUTE, CompletedOn, GETUTCDATE()) >= +CONVERT(VARCHAR(30), @PatientChartLockingInterval) 
          AND (PatientCharts.CompletedOn IS NOT NULL) 
       ) 
SELECT PatientCharts.VisitNumber , 
     PatientChartImages.ImageSequence AS ImageSequence 
FROM dbo.PatientChartImagesCorporate AS PatientChartImages WITH (READPAST) 
     INNER JOIN DirectPatientChartCTE AS PatientCharts ON PatientChartImages.PatientChartId = PatientCharts.PatientChartId 
WHERE Patientchartimages.OnbasedDate IS NULL 
UNION ALL 
(SELECT PatientCharts.VisitNumber , 
      PatientChartImages.ImageSequence AS ImageSequence 
    FROM  dbo.PatientChartImages AS PatientChartImages WITH (READPAST) 
      INNER JOIN RemotePatientChartCTE AS PatientCharts ON PatientChartImages.PatientChartId = PatientCharts.PatientChartId 
    WHERE  Patientchartimages.OnbasedDate IS NULL 
) 
    ) 

我定義了兩個CTE，DirectPatientChartCTE和RemotePatientChartCTE。如果0記錄由RemotePatientChartCTE返回，我不想使用union。

據我所知，我可以在查詢下使用union子語中的where子句來檢查CTE中的0條記錄。在這種情況下，第二個查詢也會被評估。如果記錄不存在，我不希望第二個查詢中的表進行掃描。

這已經從一個視圖更改爲內聯TVF，因爲視圖的性能很糟糕。我不能使用SP，因爲我必須用這個TVF的結果填充動態臨時表。請建議。

Answer 1

你可以把你的函數變成一個多語句表值函數。一次執行CTE中的查詢，並將每個查詢的結果存儲在表變量中。然後，您可以檢查第二個表變量中的行數，並在必要時執行聯合查詢。

在僞代碼這樣的東西。

declare @Direct table 
(
    PatientChartID int primary key, 
    VisitNumber int 
) 

declare @Remote table 
(
    PatientChartID int primary key, 
    VisitNumber int 
) 

insert into @Direct 
select top 500 VisitNumber,PatientChartID 
from PatientChartCorporate 
--where .... 

insert into @Remote 
select top 500 VisitNumber,PatientChartID 
from PatientChartCorporate 
--where .... 

if exists(select * from @Remote) 
begin 
    -- union query here 

end 
else 
begin 
    -- non union query here 

end