SQL> create table table_log (timestamp date);

Table created.

SQL> insert into table_log values (sysdate);

1 row created.

SQL> commit;

Commit complete.

SQL> select * from table_log;

TIMESTAMP
---------
15-NOV-02

SQL> select to_char(timestamp, 'dd-mon-yyyy hh24:mi:ss') from table_log;

TO_CHAR(TIMESTAMP,'D
--------------------
15-nov-2002 11:03:04

SQL> alter session set nls_date_format = 'dd-mon-yyyy hh24:mi:ss'
  2  /

Session altered.

SQL> select * from table_log;

TIMESTAMP
--------------------
15-nov-2002 11:03:04