Oracle月份？

oracle獲得上個月的月份：select to_char(add_months(trunc(sysdate),-1),'yyyymm') from dual;oracle獲得下個月的月份：select to_char(add_months(trunc(sysdate),1),'yyyymm') from dual;oracle獲得上個月的第一天日期：select data_dt ,ADD_MONTHS(TRUNC( to_date(data_dt, 'YYYY-MM-DD'),'MM' ),-1) from a_web_visit_origin;oracle獲得上個月的第一天日期（符合當地的日期格式）：select data_dt ,TO_CHAR (ADD_MONTHS(TRUNC( to_date(data_dt, 'YYYY-MM-DD'),'MM' ),-1),'YYYY-MM-DD') from a_web_visit_origin;oracle獲得上個月當天日期：select data_dt ,TO_CHAR (ADD_MONTHS(TRUNC( to_date(data_dt, 'YYYY-MM-DD') ),-1),'YYYY-MM-DD') from a_web_visit_origin;select data_dt ,ADD_MONTHS(TRUNC( to_date(data_dt, 'YYYY-MM-DD'),'MM' ),-1) from a_web_visit_origin;oracle獲得上個月的第一天日期（符合當地的日期格式）：select data_dt ,TO_CHAR (ADD_MONTHS(TRUNC( to_date(data_dt, 'YYYY-MM-DD'),'MM' ),-1),'YYYY-MM-DD') from a_web_visit_origin;oracle獲得上個月當天日期：select data_dt ,TO_CHAR (ADD_MONTHS(TRUNC( to_date(data_dt, 'YYYY-MM-DD') ),-1),'YYYY-MM-DD') from a_web_visit_origin;擴展資料：日期和字符轉換函數用法（to_date,to_char）：日期轉化為字符串：select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as nowTime from dual;獲取時間的年： select to_char(sysdate,'yyyy') as nowYear from dual; 獲取時間的月： select to_char(sysdate,'mm') as nowMonth from dual;獲取時間的日：select to_char(sysdate,'dd') as nowDay from dual;獲取時間的時：select to_char(sysdate,'hh24') as nowHour from dual;獲取時間的分：select to_char(sysdate,'mi') as nowMinute from dual; 獲取時間的秒：select to_char(sysdate,'ss') as nowSecond from dual;