Convert IIF Access SQL to Oracle SQL...

Question

I am in the process of converting a MS Access application to VB.Net with Oracle database behind. However I am having a problem converting an MS Access Query that contains IIF statements into an Oracle SQL command. Below is the MS Access SQL code:
SELECT PDTABLE_132.UNIQUE_CLASH_ID, CISClashStatusTbl.Approval_Type AS Clash_Status, CISClashTypeTbl.Clash_Type, *IIf([TEMP_ACTION_DISCIPLINE] Is Null,"UNALOCATED",[TEMP_ACTION_DISCIPLINE]) AS ACTION_DISCIPLINE*, *IIf([CISDisciplineTbl].[Discipline] Is Null,[PD_2910A_PDTABLE_111].[DISCIPLINE_NAME],[CISDisciplineTbl].[Discipline]) AS TEMP_ACTION_DISCIPLINE*
FROM ((((((((((((PDTABLE_132 INNER JOIN PD_2910A_PDTABLE_113 ON PDTABLE_132.MODEL_INDEX_NO_A = PD_2910A_PDTABLE_113.MODEL_INDEX_NO) INNER JOIN PD_2910A_PDTABLE_113 AS PD_2910A_PDTABLE_113_1 ON PDTABLE_132.MODEL_INDEX_NO_B = PD_2910A_PDTABLE_113_1.MODEL_INDEX_NO) INNER JOIN PDTABLE_119 ON PD_2910A_PDTABLE_113.MODEL_INDEX_NO = PDTABLE_119.MODEL_INDEX_NO) INNER JOIN PDTABLE_119 AS PDTABLE_119_1 ON PD_2910A_PDTABLE_113_1.MODEL_INDEX_NO = PDTABLE_119_1.MODEL_INDEX_NO) LEFT JOIN CISClashStatusTbl ON PDTABLE_132.IF_APPROVAL_STATUS = CISClashStatusTbl.Approval_Code) LEFT JOIN CISClashTypeTbl ON PDTABLE_132.RECENT_CLASH_TYPE = CISClashTypeTbl.Clash_Code) INNER JOIN PD_2910A_PDTABLE_112 ON PD_2910A_PDTABLE_113.AREA_INDEX_NO = PD_2910A_PDTABLE_112.AREA_INDEX_NO) INNER JOIN PD_2910A_PDTABLE_112 AS PD_2910A_PDTABLE_112_1 ON PD_2910A_PDTABLE_113_1.AREA_INDEX_NO = PD_2910A_PDTABLE_112_1.AREA_INDEX_NO) LEFT JOIN CISOwnerTbl ON PDTABLE_132.UNIQUE_CLASH_ID = CISOwnerTbl.UNIQUE_CLASH_ID) LEFT JOIN CISDisciplineTbl ON CISOwnerTbl.Discipline_Code = CISDisciplineTbl.Discipline_Code) LEFT JOIN PD_2910A_PDTABLE_111 ON PDTABLE_132.ACTION_DISCIPLINE = PD_2910A_PDTABLE_111.DISCIPLINE_INDX_NO) LEFT JOIN PD_2910A_PDTABLE_111 AS PD_2910A_PDTABLE_111_1 ON PDTABLE_132.DISCIPLINE_INDEX_A = PD_2910A_PDTABLE_111_1.DISCIPLINE_INDX_NO) LEFT JOIN PD_2910A_PDTABLE_111 AS PD_2910A_PDTABLE_111_2 ON PDTABLE_132.DISCIPLINE_INDEX_B = PD_2910A_PDTABLE_111_2.DISCIPLINE_INDX_NO
ORDER BY PDTABLE_132.UNIQUE_CLASH_ID;
Any help would really be appreshiated.
Thanks in advance
Simon
Edited by: user8275408 on 21-Jan-2010 07:25

Answer 1

Hi, Simon,
Welcome to the forum!
An Oracle equivalent of
IIf(TEMP_ACTION_DISCIPLINE Is Null,"UNALOCATED",TEMP_ACTION_DISCIPLINE) AS ACTION_DISCIPLINEis
CASE
     WHEN  TEMP_ACTION_DISCIPLINE Is Null
     THEN  'UNALOCATED'
     ELSE  TEMP_ACTION_DISCIPLINE
END          AS ACTION_DISCIPLINE, This assumes that temp_action_discipline is a string. (All THEN and ELSE clauses must return the same data type, or at least compatable types.)
CASE is the most general way of doing IF-THE-ELSE logic in Oracle SQL.
For certain special situations, there may be shorter ways.
Testing a variable to see whether it is NULL or not is one of those situations, so you could also say
NVL2 ( TEMP_ACTION_DISCIPLINE
     , TEMP_ACTION_DISCIPLINE
     , 'UNALOCATED'
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Edited by: Frank Kulash on Jan 21, 2010 10:41 AM
After reading Bluefrog's answer, I realized that you're testing and possibly returning the same thing, temp_action_discipline.
In that case, NVL, like Bluefrog suggested, is the best thing to do.  CASE and NVL2, as shown above, will give the right results, but they're more complicated than you need for this job.