oracle not exists效率比not in高

select count(1) from t1 a where not exists (select null from t2 b where b.no = a.uuid)

与

select * from t1 a where a.proxyid not in (
select c.proxyid from t2 b,t1 c where b.no = c.uuid)

功能一样，但not exists效率比not in高