mysql> SELECT distinct habitant.nom from habitant,menhir,manger where ((habitant.nom = menhir.nom)) OR (habitant.nom = manger.nom);
+-----------------+
| nom             |
+-----------------+
| astrix          |
| panoramix       |
| assurancetourix |
| cetautomatix    |
| oblix           |
| ordrealphabetix |
+-----------------+
6 rows in set (0.00 sec)