12小时制的nls_date_format hh:mi:ss默认是12小时制
SQL> alter session set nls_date_format='yyyy-mm-dd hh12:mi:ss';
Session altered.
SQL> select sysdate from dual;
SYSDATE
-------------------
2007-01-09 01:56:10
SQL> alter session set nls_date_format='yyyy-mm-dd hh:mi:ss';
Session altered.
SQL> select sysdate from dual;
SYSDATE
-------------------
2007-01-09 01:56:24
SQL> alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';
Session altered.
SQL> select sysdate from dual;
SYSDATE
-------------------
2007-01-09 13:56:38
SQL> alter session set nls_date_format='yyyy-mm-dd hh:mi:ss';
Session altered.
SQL> select sysdate from dual;
SYSDATE
-------------------
2007-01-09 01:56:48
SQL> alter session set nls_date_format='yyyy-mm-dd hh:mi:ss pm';
Session altered.
SQL> select sysdate from dual;
SYSDATE
----------------------
2007-01-09 01:56:58 pm
SQL> alter session set nls_date_format='yyyy-mm-dd hh:mi:ss am';
Session altered.
SQL> select sysdate from dual;
SYSDATE
----------------------
2007-01-09 01:57:10 pm
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