Assistance with Access ADP and/or SQL iif statement

Question

I'm using Access ADP as a front end to SQL. I have two tables:

• One is Price_2018
• One is Price_2020

I want to choose Price from the Price_2018 or the Price_2020 table, depending upon the Purchase_Date. I tried first putting IiF statement in the Query Designer:

Iif ([Purchase_Date] < Convert(DateTime, '2020-01-01 00:00:00'),[Price_2018],[Price_2020])

Access didn't allow that and ended up putting the whole thing in quotes in the SQL pane, so all I got was text output.

Someone suggested putting in the Select section:

CASE ([Purchase_Date] < CONVERT(DATETIME, '2020-01-01 00:00:00')   WHEN 1 THEN [Price_2018] ELSE [Price_2020] 

That didn't work either and gave me this error:

Error in list of function arguments: '<' not recognized.Error in list of function arguments: ',' not recognized.Error in list of function arguments: 'FROM' not recognized.
Unable to parse query text.

How to resolve this error. I'm not familiar with using a CASE statement in Access or SQL.

I combined 2 Price tables (combined table called VWC_2018_2020) as suggested. Full query:

SELECT      TOP 100 PERCENT dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_ID,                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_Date_From, dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Update_Status,                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Account_Number, dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_Units,                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Modifiers, dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Procedure_Code,                         NormalUnionCPASumAdjustments.SumAmount AS Adjustment, NormalUnionCPASumPayments.SumAmount AS Payment,                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_Fee AS Charge,                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_Fee - ISNULL(NormalUnionCPASumPayments.SumAmount, 0) AS Unpaid,                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Primary_Diagnosis_Code, LastInsurancePmt.last_insurance_pmt,                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Patient_Number, dbo.VWCFees_2018_2020.VWC_2020, dbo.VWCFees_2018_2020.VWC_2018,                        IIF (dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_Date_From < CDate('2020-01-01 00:00:00'),dbo.VWCFees_2018_2020.VWC_2018,dbo.VWCFees_2018_2020.VWC_2020) AS VWCFEE
FROM          dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo LEFT OUTER JOIN                        dbo.VWCFees_2018_2020 ON dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Procedure_Code = dbo.VWCFees_2018_2020.CPT LEFT OUTER JOIN                        dbo.NormalUnionCPASumAdjustments() NormalUnionCPASumAdjustments ON                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_ID = NormalUnionCPASumAdjustments.Service_ID LEFT OUTER JOIN                        dbo.NormalUnionCPASumPayments() NormalUnionCPASumPayments ON                         dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_ID = NormalUnionCPASumPayments.Service_ID LEFT OUTER JOIN                        dbo.LastInsurancePmt() LastInsurancePmt ON dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_ID = LastInsurancePmt.Service_ID
WHERE      (dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Update_Status <= 1) AND                         (dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Service_Date_From BETWEEN @StartDate AND @EndDate) AND                         (dbo.VHCSERVER_Ntier_VHC_dbo_vwGenSvcInfo.Patient_Number = @VHC_NumberChild)

Running in Access, gives error message: '<' not recognized. Missing FROM clause. Unable to parse query text.

What now? Thanks

Answer 1

Since ADP files use an SQL Server backend (no longer supported as of MS Access 2013), you must use its TSQL dialect which does support IIF (or CASE ) and can compare dates with string representations without conversion.

Below I extend to fuller query assuming various columns. Adjust as needed:

SELECT
  ...
  IIF(t.[Purchase_Date] < '2020-01-01', p18.price, p20.price)
  ...
FROM [Transactions] t
INNER JOIN [Price_2018] p18
  ON t.price_id = p18.price_id
INNER JOIN [Price_2020] p20
  ON t.price_id = p20.price_id