-- Uvazujte databazu OsobaVztah

USE OsobaVztah;

-- Vratte id deti a id ich rodicov do dvoch stlpcov.

-- Tri riesenia:

-- Riesenie A:

SELECT id, matka FROM Osoba WHERE matka is not null
union all
SELECT id, otec FROM Osoba WHERE otec is not null
ORDER BY id;

-- Riesenie B:


WITH DieRod(idD, idR)
AS(
SELECT id, matka FROM Osoba WHERE matka is not null
union all
SELECT id, otec FROM Osoba WHERE otec is not null
)
SELECT * FROM DieRod ORDER BY idD;

-- Riesenie C:

SELECT D.id, R.id FROM Osoba AS D
 JOIN Osoba R
      ON D.id IN(R.matka, R.otec)
      --  ON R.id IN(D.matka, D.otec)