Suggested SQL query

Question

Hi
I need you help for suggesting a query. These are the two tables :
CREATE TABLE  "RENCONTRE"
   (     "NUMPERS1" NUMBER,
     "NUMPERS2" NUMBER,
     "DATE_R" DATE,
     "NUMLIEU" NUMBER,
     "RESULTAT" VARCHAR2(20),
      CONSTRAINT "RENCONTRE_PK" PRIMARY KEY ("NUMPERS1", "NUMPERS2", "DATE_R") ENABLE
ALTER TABLE  "RENCONTRE" ADD CONSTRAINT "RENCONTRE_FK" FOREIGN KEY ("NUMLIEU")
       REFERENCES  "LIEU" ("NUMLIEU") ENABLE
CREATE TABLE  "PERSONNE"
   (     "NUMPERS" NUMBER,
     "NOM" VARCHAR2(50),
     "PRENOM" VARCHAR2(50),
     "ADRESSE" VARCHAR2(128),
     "TELEPHONE" VARCHAR2(64),
     "SEXE" VARCHAR2(20),
      CONSTRAINT "PERSONNE_PK" PRIMARY KEY ("NUMPERS") ENABLE
INSERT INTO PERSONNE (Numpers,Nom,Prenom,Adresse,Telephone,Sexe) values
(1,'Delval','Bruno','Rue de la Fantaisie','06 52 45 89','masculin');
INSERT INTO PERSONNE (Numpers,Nom,Prenom,Adresse,Telephone,Sexe) values (2,'Jolie','Emily','30 rue de arc en ciel','06 25 89 45','feminin');
INSERT INTO PERSONNE (Numpers,Nom,Prenom,Adresse,Telephone,Sexe) values (4,'Dufour','Coralie','97 avenue du Four','05 78 46 89','feminin');
INSERT INTO PERSONNE (Numpers,Nom,Prenom,Adresse,Telephone,Sexe) values (3,'Judoper','Marcel','23 rue de la resistance','06 89 45 78','masculin');
INSERT INTO RENCONTRE (NUMPERS1,NUMPERS2,DATE_R,NUMLIEU,RESULTAT) VALUES (1,2,TO_DATE('01/20/2007', 'DD/MM/YYYY'),1, 'positif');
INSERT INTO RENCONTRE (NUMPERS1,NUMPERS2,DATE_R,NUMLIEU,RESULTAT) VALUES (3,4,TO_DATE('01/15/2006', 'DD/MM/YYYY'),2,'negatif');
INSERT INTO RENCONTRE (NUMPERS1,NUMPERS2,DATE_R,NUMLIEU,RESULTAT) VALUES (2,4,TO_DATE('01/01/0007', 'DD/MM/YYYY'),4,’positif’);The table RENCONTRE contains the NUMPERS of people who had met another person (NUMPERS1 and NUMPERS2 of the table RENCONTRE)
NUMPERS1 and NUMPERS2 refers to NUMPERS of the table PERSONNE.
Expected result of the query :
Name of the people (column 'NOM' of table PERSONNE) who never had met a person of the same gender ('SEXE')
NOM
Judoper
Thank you for your kind help.
Christian

Answer 1

The foreign key might be correctly intended, but we don't have the table it refers to.
But anyway, that's a side note, how about:
SQL> select p.nom
  2  from   personne p
  3  where  not exists ( select null
  4                      from   rencontre r
  5                      ,      personne p2
  6                      where  r.numpers1 = p.numpers
  7                      and    p2.numpers != p.numpers
  8                      and    p2.numpers = r.numpers2
  9                      and    p2.sexe = p.sexe
10                    )
11  and    not exists ( select null
12                      from   rencontre r
13                      ,      personne p2
14                      where  r.numpers1 != p.numpers
15                      and    p2.numpers = p.numpers
16                      and    p2.numpers = r.numpers2
17                      and    p2.sexe = p.sexe
18                    );
NOM
Delval
Judoper
2 rows selected.