plsql advanced or condition

Question

I have a table containing post adresses. my query looks like this:

SELECT "ID", postcode, numbertype, minnumber, maxnumber
INTO huidigPostcodeID_FK, databasePostcode, databaseNumberType, databaseMinNumber, databaseMaxNumber
FROM POSTCODE 
WHERE POSTCODE_ID = 79417568 AND (NUMBERTYPE = 'odd' OR NUMBERTYPE = 'mixed')

In most cases this works fine since it has to deliver 1 row only. in the case when there are 2 identical recors (one with numbertype = odd and the other mixed) the query returns 2 rows.

        ID POSTCODE NUMBERTYPE  MINNUMBER  MAXNUMBER
---------- -------- ---------- ---------- ----------
    395755 7941KD   odd                 9          9 
    395756 7941KD   mixed               1         22 

I don't want this because I get an error by this. Has somebody a solution wherein the programm only gets one record with numbertype = 'mixed' in it?

So in the above example I only wan't this record to show up:

    ID POSTCODE NUMBERTYPE  MINNUMBER  MAXNUMBER

---

395756 7941KD   mixed               1         22 

Answer 1

I think one might also use a window function to accomplish this:

SELECT "ID", postcode, numbertype, minnumber, maxnumber
  INTO huidigPostcodeID_FK, databasePostcode, databaseNumberType, databaseMinNumber, databaseMaxNumber
  FROM (
    SELECT "ID", postcode, numbertype, minnumber, maxnumber
         , ROW_NUMBER() OVER ( PARTITION BY postcode ORDER BY DECODE(numbertype, 'mixed', 0, 1) ) AS rn
      FROM postcode
     WHERE postcode_id = 79417568 AND (numbertype = 'odd' OR numbertype = 'mixed')
) WHERE rn = 1

In this case, if there are two records for a given value of postcode, it will select the one where the value of numbertype is 'mixed'. One might also simply use ORDER BY numbertype in the OVER( ) clause but that's not as explicit in saying that 'mixed' ought to come first.

Hope this helps.