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-- to_char()只是将日期数据以怎样的格式显示出来,要截取日期,可以用trunc()函数,
-- 实例如下:
sys@SZTYORA> conn / as sysdba
已连接。
sys@SZTYORA> alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';
会话已更改。
sys@SZTYORA> select sysdate from dual;
SYSDATE
-------------------
2011-02-09 10:43:32
sys@SZTYORA> select trunc(sysdate) from dual;
TRUNC(SYSDATE)
-------------------
2011-02-09 00:00:00
sys@SZTYORA> select trunc(sysdate,'mm') from dual;
TRUNC(SYSDATE,'MM')
-------------------
2011-02-01 00:00:00
sys@SZTYORA> select trunc(sysdate,'yyyy') from dual;
TRUNC(SYSDATE,'YYYY
-------------------
2011-01-01 00:00:00
sys@SZTYORA> select trunc(sysdate,'ww') from dual;
TRUNC(SYSDATE,'WW')
-------------------
2011-02-05 00:00:00
SQL> SELECT extract(YEAR FROM SYSDATE) ||
2 lpad(extract(MONTH FROM SYSDATE), 2, '0')
3 FROM dual;
EXTRACT(YEARFROMSYSDATE)||LPAD
--------------------------------------------
201101
SQL>
SQL> SELECT extract(YEAR FROM SYSDATE) || extract(MONTH FROM SYSDATE) FROM dual;
EXTRACT(YEARFROMSYSDATE)||EXTR
--------------------------------------------------------------------------------
20111
SQL>