sql - 查找 systime 是否介于两次之间 -oracle sql

Question

更新

基本上，我正在尝试创建一个触发器，它限制对表 b/w 晚上 9 点和上午 9 点的任何更改。这里是示例。

CREATE OR REPLACE TRIGGER courses_biud
before insert or update or delete 
on courses 
begin
if to_char(sysdate,'hh24') between **{9 p.m and 9.am}** Then 
...
end ;

Answer 1

select to_char(sysdate,'hh24') || ' is in the timeframe'  as result
from dual
where to_char(sysdate,'hh24') > 21
or to_char(sysdate,'hh24') < 9