oracle查询截至到当前日期月份所在年份的所有月份

SELECT to_number(TO_CHAR(add_months(trunc(sysdate, 'yy'), ROWNUM - 1), 'MM')) as month FROM DUALCONNECT BY ROWNUM <= (select months_between(trunc(sysdate, 'mm'), trunc(sysdate, 'yy')) + 1 from dual);

/**************日期********************/select trunc(sysdate) from dual --2013-01-06 今天的日期为2013-01-06select trunc(sysdate, 'mm') from dual --2013-01-01 返回当月第一天.select trunc(sysdate,'yy') from dual --2013-01-01 返回当年第一天select trunc(sysdate,'dd') from dual --2013-01-06 返回当前年月日select trunc(sysdate,'yyyy') from dual --2013-01-01 返回当年第一天select trunc(sysdate,'d') from dual --2013-01-06 (星期天)返回当前星期的第一天select trunc(sysdate, 'hh') from dual --2013-01-06 17:00:00 当前时间为17:35 select trunc(sysdate, 'mi') from dual --2013-01-06 17:35:00 TRUNC()函数没有秒的精确/***************数字********************//*TRUNC（number,num_digits） Number 需要截尾取整的数字。 Num_digits 用于指定取整精度的数字。Num_digits 的默认值为 0。TRUNC()函数截取时不进行四舍五入*/select trunc(123.458) from dual --123.select trunc(123.458,0) from dual --123.select trunc(123.458,1) from dual --123.4.select trunc(123.458,-1) from dual --120.select trunc(123.458,-4) from dual --0.select trunc(123.458,4) from dual --123.458.select trunc(123) from dual --123.select trunc(123,1) from dual --123.select trunc(123,-1) from dual --120