assoc.sql

SELECT NumPil, NumAv
FROM   Vols
WHERE  NumPil IS NOT NULL AND NumAv IS NOT NULL
GROUP BY NumPil, NumAv
ORDER BY NumPil;

gistfile2.txt

AVIONS (#NumAv, NomAv, CapAv, VilleAv)
PILOTES (#NumPil, NomPil, NaisPil, VillePil)
VOLS (#NumVol, VilleD, VilleA, DateD, DateA, NumPil, NumAv, CoutVol)

la_requete_gagnante.sql

SELECT NumPil, COUNT(*)
FROM   (
  SELECT NumPil, NumAv
  FROM   Vols
  WHERE  NumPil IS NOT NULL AND NumAv IS NOT NULL
  GROUP BY NumPil, NumAv
  ORDER BY NumPil
)
GROUP BY NumPil;