SQL> select count(*) From dual connect by level < 1E6;

  COUNT(*)
----------
    999999

Elapsed: 00:00:01.56
SQL>

SQL*Plus: Release 11.2.0.1.0 Production on Mon May 26 15:06:14 2014

Copyright (c) 1982, 2010, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning and Automatic Storage Management options

SQL> timing show;
SP2-0325: no timing elements to show
SQL> timing start t_start;
SQL> timing show;
timing for: t_start
Elapsed: 00:00:06.94
SQL> timing start t_start_2;
SQL> timing show;
timing for: t_start_2
Elapsed: 00:00:03.86
SQL> timing stop;
timing for: t_start_2
Elapsed: 00:00:10.77
SQL> timing show;
timing for: t_start
Elapsed: 00:01:04.20
SQL> timing stop;
timing for: t_start
Elapsed: 00:01:08.96
SQL> timing show;
SP2-0325: no timing elements to show
SQL>

SQL> set timing on
SQL> select count(*) from dual connect by level < 600000;
  COUNT(*)
----------
    599999

1 row selected.

Elapsed: 00:00:00.26

SQL> set timing on
SQL> select count(*) from dual connect by level < 600000;
  COUNT(*)
----------
    599999

1 row selected.

Elapsed: 00:00:00.26