Selecting rows with null values in an sql 3 table

Question

Hi everyone I use oracle database 11g and have the following SQL statement:
SELECT Oprema.Opr_Id, Oprema.Datum_Nabavke, Oprema.Datum_Zaduzenja, Oprema.Dobavljac, Oprema.Jedinica_Mjere,
     coalesce ((Oprema.Zaduzio), 0), Oprema.Vrijednost, Oprema.Kolicina_Nabavna, Oprema.Kolicina_Otpisana, Oprema.Kolicina_Trenutna, Oprema.Status, Oprema.Konto,
     Oprema.KontoIsp, Oprema.Broj_Naloga, Oprema.Sifra_Objekta, Dobavljaci.Naziv AS DobNaz, coalesce(to_char(Uposlenici.Prezime), 'hm'), Objekti.Objekat_ID
FROM OPREMA Oprema, UPOSLENICI Uposlenici, DOBAVLJACI Dobavljaci, OBJEKTI Objekti
WHERE  Oprema.Dobavljac=Dobavljaci.Dob_Id AND Oprema.Zaduzio=Uposlenici.UposlenikId AND Oprema.Sifra_Objekta=Objekti.Objekat_IDWhat I need is to show all the rows in the database. The problem is that some of the foreign keys Zaduzio and Objekti are NULL. This means the databse won't show those and only shows me rows where both have values. In all of these rows except for 3 only one of the two foreign keys has a value.
So what I need is an sql that would show me all 3. As you can see I tried with Coallesce but it didn't work, still only 3 rows show.
I also tried with UNION
SELECT Oprema.Opr_Id, Oprema.Datum_Nabavke, Oprema.Datum_Zaduzenja, Oprema.Dobavljac, Oprema.Jedinica_Mjere,
     Oprema.Zaduzio, Oprema.Vrijednost, Oprema.Kolicina_Nabavna, Oprema.Kolicina_Otpisana, Oprema.Kolicina_Trenutna, Oprema.Status, Oprema.Konto,
     Oprema.KontoIsp, Oprema.Broj_Naloga, Oprema.Sifra_Objekta, Dobavljaci.Naziv AS DobNaz, Uposlenici.Prezime, Objekti.Objekat_ID
FROM OPREMA Oprema, UPOSLENICI Uposlenici, DOBAVLJACI Dobavljaci, OBJEKTI Objekti
WHERE  Oprema.Dobavljac=Dobavljaci.Dob_Id AND Oprema.Zaduzio=Uposlenici.UposlenikId AND Oprema.Sifra_Objekta=Objekti.Objekat_IDBut then the rows that have both Zaduzio and Objekti values are multiplied and selected twice.
So any ideas on how to do this?

Answer 1

Hi,
If those foreign keys are NULL, then an inner join won't produce any results. Maybe you need to make it an outer-join, like this:
SELECT  Oprema.Opr_Id
,      Oprema.Datum_Nabavke
,      Oprema.Datum_Zaduzenja
,      Oprema.Dobavljac
,      Oprema.Jedinica_Mjere
,     COALESCE ( Oprema.Zaduzio
           , 0
           )          AS zaduzio_or_0
,      Oprema.Vrijednost
,      Oprema.Kolicina_Nabavna
,      Oprema.Kolicina_Otpisana
,      Oprema.Kolicina_Trenutna
,      Oprema.Status
,      Oprema.Konto,
     Oprema.KontoIsp
,      Oprema.Broj_Naloga
,      Oprema.Sifra_Objekta
,      Dobavljaci.Naziv     AS DobNaz
,      COALESCE ( TO_CHAR (Uposlenici.Prezime)
           , 'hm'
           )          AS prezime_or_hm
,      Objekti.Objekat_ID
FROM            OPREMA
JOIN            DOBAVLJACI  ON   Oprema.Dobavljac      = Dobavljaci.Dob_Id
LEFT OUTER JOIN      UPOSLENICI  ON       Oprema.Zaduzio     = Uposlenici.UposlenikId
LEFT OUTER JOIN  OBJEKTI     ON       Oprema.Sifra_Objekta  = Objekti.Objekat_ID
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all the tables involved, and the results you want from that data.
Simplify the problem. For example, if you really need to display 18 columns, but 15 of them have nothing to do with the problem, then post a question that just includes e or 4 of those columns.
Explain, using specific examples, how you get those results from that data.
Always say what version of Oracle you're using (e.g. 11.2.0.2.0).
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