ORA-01036: 非法的变量名/编号

CREATE OR REPLACE TRIGGER site_triggers
BEFORE INSERT ON TSITEINFO FOR EACH ROW  WHEN (new.id is null)

BEGIN
       SELECT INID.NEXTVAL INTO :NEW.id FROM DUAL;
END;
请问上面这句哪个变量名非法，表名TSITEINFO没有任何问题