-- 不考虑周六、日及节假日的话，可以简单这样写：
SELECT (case when to_char(sysdate,'HHMI')<'0800' OR to_char(sysdate,'HHMI')>'1700' 
             then '非上班时间'
             else '上班时间' end) as "现在是否为上班时间"
FROM dual;

------解决方案--------------------
探讨


 to_char(sysdate,'hh24') between '08' and '17'


------解决方案--------------------
SQL code

select case
                 when to_char(sysdate, 'hh24miss') between '080000' and '165959' then
                    '上班时间'
                 else
                    '下班时间'
             end
from   dual;