setting up unique constraint on referenced collumns in oracle 10g xe

Question

hi, i have the following situation.

table looks like this

CREATE TABLE CompetitionsLanguages (
  competition REF CompetitionType SCOPE IS Competitions,
  language REF LanguageType SCOPE IS Languages
);

i need this table to have a unique constraint on (competition,language) combination. oracle tells me that i cant put a UNIQUE or PK on collumns that reference other tables.

is it possible to somehow avoid the unique, using the CHECK, or some sort of a TRIGGER?

thank you

Answer 1

CREATE UNIQUE INDEX unqIndex
    ON CompetitionsLanguages(CompetitionsLanguages, CompetitionsLanguages);