SELECT
col1,col2
FROM T1
WHERE T1.col3=( SELECT
                MAX(col4)
                FROM T1 )

v := SELECT MAX(col4)FROM T1
SELECT
col1,col2
FROM T1
WHERE T1.col3 = v

create table test_0100 (col_1  number, col_2 number);

insert into test_0100 select level, mod(level,floor(level/2)) from dual connect by level <= 10000;

declare
  v_iter  pls_integer := 10000;
  v_time  pls_integer;
  v_max   pls_integer;
  v_res   varchar2(1);
begin
  v_time := dbms_utility.get_time;
  
  for i in 1..v_iter loop
    SELECT col_2
    into   v_res
    FROM   test_0100
    WHERE  col_1=( SELECT MAX(col_1)
                   FROM   Test_0100 );
  end loop; 
  
  dbms_output.put_line('One query '||to_char(dbms_utility.get_time - v_time));

  for i in 1..v_iter loop
    select max(col_1) into v_max from test_0100;
    
    select col_2 into v_res from test_0100 where col_1 = v_max;
  end loop;
  
  dbms_output.put_line('Two Queries '||to_char(dbms_utility.get_time - v_time));

end;
/


One query 2455
Two Queries 4183