Oracle里时间的应用

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-11:00 12-11月-03 04.59.13.668000 下午 -11:
                00

SQL>

3、current_timestamp()以timestamp with time zone数据类型返回当前会放时区中的当前日期
timestamp_with_time_zone_value:=current_timestamp([timestamp_precision])
SQL> column sessiontimezone for a15
SQL> column current_timestamp format a36
SQL> select sessiontimezone,current_timestamp from dual;

SESSIONTIMEZONE CURRENT_TIMESTAMP
--------------- ------------------------------------
+08:00 13-11月-03 11.56.28.160000 上午 +08:
                00

SQL> alter session set time_zone=''''-11:00''''
  2 /

会话已更改。

SQL> select sessiontimezone,current_timestamp from dual;

SESSIONTIMEZONE CURRENT_TIMESTAMP
--------------- ------------------------------------
-11:00 12-11月-03 04.58.00.243000 下午 -11:
                00

SQL>

4、dbtimezone()返回时区
varchar_value:=dbtimezone
SQL> select dbtimezone from dual;

DBTIME
------
-07:00

SQL>

5、extract()找出日期或间隔值的字段值
date_value:=extract(date_field from [datetime_value|interval_value])
SQL> select extract(month from sysdate) "This Month" from dual;

This Month
----------
        11

SQL> select extract(year from add_months(sysdate,36)) "3 Years Out" from dual;

3 Years Out
-----------
       2006

SQL>

6、last_day()返回包含了日期参数的月份的最后一天的日期
date_value:=last_day(date_value)
SQL> select last_day(date''''2000-02-01'''') "Leap Yr?" from dual;

Leap Yr?
----------
29-2月 -00

SQL> select last_day(sysdate) "Last day of this month" from dual;

Last day o
----------
30-11月-03

SQL>

7、localtimestamp()返回会话中的日期和时间
timestamp_value:=localtimestamp
SQL> column localtimestamp format a28
SQL> select localtimestamp from dual;

LOCALTIMESTAMP
----------------------------
13-11月-03 12.09.15.433000
下午

SQL> select localtimestamp,current_timestamp from dual;

LOCALTIMESTAMP CURRENT_TIMESTAMP
---------------------------- ------------------------------------
13-11月-03 12.09.31.006000 13-11月-03 12.09.31.006000 下午 +08:
下午 00

SQL> alter session set time_zone=''''-11:00'''';

会话已更改。

SQL> select localtimestamp,to_char(sysdate,''''DD-MM-YYYY HH:MI:SS AM'''') "SYSDATE" from dual;

LOCALTIMESTAMP SYSDATE
---------------------------- ------------------------
12-11月-03 05.11.31.259000 13-11-2003 12:11:31 下午
下午

SQL>

8、months_between()判断两个日期之间的月份数量
number_value:=months_between(date_value,date_value)
SQL> select months_between(sysdate,date''''1971-05-18'''') from dual;

MONTHS_BETWEEN(SYSDATE,DATE''''1971-05-18'''')
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   &nbs