oracle 获取时间

1、获取当前时间的前24小时的各小时时间段

select
    to_char(to_date(to_char(sysdate - (rownum - 1) / 24,'yyyy-mm-dd hh24')
                        || ':00:00','yyyy-mm-dd hh24:mi:ss'),'yyyy-mm-dd hh24:mi:ss') totaldate
from
    dual
connect by
    rownum <= 24
order by
    totaldate desc

2、获取某天的0点到24点的各小时时间段

select
    TO_CHAR(to_date('2019-01-28','yyyy-mm-dd') + (rownum - 1) / 24,'yyyy-mm-dd hh24:mi:ss') TIMES
from
    DUAL
connect by
    level <= 24

3、获取0点到当前时间的小时段

select
    TO_CHAR(to_date('2019-01-28','yyyy-mm-dd') + (rownum - 1) / 24,'yyyy-mm-dd hh24:mi:ss') TIMES
from
    DUAL
connect by
    level <=  to_char(sysdate + 1 / 24,'hh24')