SELECT *
  FROM users
 WHERE Lower(substr(user_fam, 1, 1))=lower(substr(user_fam, 2, 1))

select dummy, dummy from dual order by dummy;
select d.dummy, d.dummy from dual d order by d.dummy;

select r1.a, r2.b from r1 left join r2 on r1.a = r2.b where r1.id > 10 and r1.name != 'Tokio'

select r1.a, r2.b from r1 left join r2 on r1.a = r2.b where r1.id > 10 and r1.name != 'Tokio'

select r1.a, r2.b 
from (
  Select r1.a,r2.b 
  From r1 left join r2 on r1.a = r2.b 
)
where r1.id > 10 and r1.name != 'Tokio'