how much time is required to retrieve information from database containing 10M records and the table contains four columns
That is a very loose question, because it depends on so many things....but here's a trivial example done on an 3 year old laptop
SQL> create table t
2 as select rownum x1,rownum x2,rownum x3,rownum x4
3 from ( select 1 from dual connect by level <= 10000 ),
4 ( select 1 from dual connect by level <= 1000 );
Table created.
-- scanning but not fetching all the rows
SQL>
SQL>
SQL> set timing on
SQL> select max(x1) from t;
MAX(X1)
----------
10000000
Elapsed: 00:00:00.72
-- fetching every row back to the calling environment
SQL> set timing on
SQL> begin
2 for i in ( select * from t )
3 loop
4 null;
5 end loop;
6 end;
7 /
PL/SQL procedure successfully completed.
Elapsed: 00:00:11.45