Question

Following is inline table valued function

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
)
   )

I have defined two CTE, DirectPatientChartCTE and RemotePatientChartCTE. I don’t want to use union all in case 0 records are returned by RemotePatientChartCTE.

I understand that I can use a where clause in query below union all to check for 0 records in CTE. In that case also second query will be evaluated. I don’t want tables in second query to be scanned in case records don’t exist.

This has been changed from a view to inline TVF since performance with a view was horrible. I cannot use a SP since I have to fill a dynamic temporary table with the results of this TVF. Please suggest.

Answer 1

You can turn your function into a multi statement table valued function. Execute the queries in your CTE’s one at a time and store the result from each query in a table variable each. Then you can check for row count in your second table variable and do the union query if necessary.

In pseudo code something like this.

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