if 1 > (select count(*) from celebrities 
        where (professions='002' or professions like '002 %'
               or professions like '% 002' or professions like '% 002 %')
        and cel_id=X
) then
    /* Celebrity isn't an actor, so add to the end */
    update celebrities 
    set professions = '002' || case when professions is null then '' 
                                    else ' '||professions end
    where cel_id=X;
end if;