oracle 日期操作

SQL>  alter session set nls_date_format='yyyy-mm-dd Hh24:mi:ss';

Session altered.

SQL> select to_date(to_char(trunc(sysdate),'yyyy-mm-dd')||' 18:00:00','yyyy-mm-dd hh24:mi:ss')   from dual;

TO_DATE(TO_CHAR(TRU
-------------------
2019-01-25 18:00:00

select TRUNC(SYSDATE)+18/24 from dual;