Procedure om te controleren op niet-dubbele rijen in de tabel voordat ze worden ingevoegd (Oracle)

Je hebt een puntkomma na je parameterblok en je mist je IS of AS clausule:

CREATE OR REPLACE PROCEDURE add_vals (c_cntry_id OUT COUNTRIES.COUNTRY_ID%TYPE,
                                       c_cntr_name IN COUNTRIES.COUNTRY_NAME%TYPE, 
                                       c_rgn_id IN COUNTRIES.REGION_ID%TYPE)
IS
BEGIN
  INSERT INTO countries(COUNTRY_ID, COUNTRY_NAME,REGION_ID)
    values (user_seq.nextval, c_cntr_name,c_rgn_id);
  c_cntry_id := user_seq.currval;
EXCEPTION
  WHEN dup_val_on_index
  THEN 
    c_cntry_id := null;
END;
/