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1. Vsetky dvojice vlastnych sesternic
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SELECT sest1.meno || ' ' || sest1.priezvisko || ' - ' || sest2.meno || ' ' || sest2.priezvisko
FROM clovek sest1, clovek sest2, clovek rod1, clovek rod2
WHERE
  ((sest1.id_otec=rod1.id) OR (sest1.id_matka=rod1.id))
  AND
  ((sest2.id_otec=rod2.id) OR (sest2.id_matka=rod2.id))
  AND
  ((rod1.id_otec=rod2.id_otec) AND (rod2.id_matka=rod2.id_matka))
  AND sest1.pohlavie='Z' AND sest2.pohlavie='Z'
  AND sest1.id<sest2.id
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2. Pre kazdeho cloveka jeho vek v rokoch (u mrtvych pri smrti)
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SELECT 
  c.meno, 
  c.priezvisko, 
  CASE 
    WHEN c.datum_do IS NULL THEN YEAR(CURRENT DATE)-YEAR(c.datum_od)
    ELSE YEAR(c.datum_do) - YEAR(c.datum_od)
  END
FROM clovek c
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3. Roztriedte ukoncene manzelstva podla toho, ci boli rozvedene 
   alebo zanikli smrtou niektoreho manzela
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SELECT
  c1.meno, c1.priezvisko,
  c2.meno, c2.priezvisko,
  CASE
    WHEN 
      ((c1.datum_do IS NOT NULL) OR (c2.datum_do IS NOT NULL)) 
      AND
      (c1.datum_do=m.datum_do) OR c2.datum_do=m.datum_do) THEN 'zanikli smrtou'
    ELSE 'rozvedene'
  END AS ukoncene
FROM rn_manzelstvo m
JOIN rn_clovek c1 ON c1.id=m.id_manzel
JOIN rn_clovek c2 ON c2.id=m.id_manzelka
WHERE m.datum_do IS NOT NULL
ORDER BY 5