napriklad pridanim indexov na polia tabulky, ktore sa pouzivaju pri joinovani a nie su to primarne kluce?
A pokial je nickname nieco ako login, tak nan dokonca by mohol byt unique index

create index IX_USERS_1 on is_users (ID_rights);
create index IX_USERS_2 on is_users (ID_ranks);
...
create unique index UX_USERS_1 on is_users (nickname);