from http://www.itpub.net/thread-1876506-4-1.html
SQL> define
DEFINE _DATE = "20-7月 -14" (CHAR)
DEFINE _CONNECT_IDENTIFIER = "ORCL" (CHAR)
DEFINE _USER = "SYSTEM" (CHAR)
DEFINE _PRIVILEGE = "" (CHAR)
DEFINE _SQLPLUS_RELEASE = "1102000100" (CHAR)
DEFINE _EDITOR = "Notepad" (CHAR)
DEFINE _O_VERSION = "Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options" (CHAR)
DEFINE _O_RELEASE = "1102000100" (CHAR)
SQL> set sqlprompt _DATE>
20-7月 -14>alter session set nls_date_format=‘YYYY-MM-DD HH:MI:SS‘;
会话已更改。
2014-07-20 12:54:33>