问题
anyone able to tell me how often a materialized view is set to refresh with the following setting plz?
REFRESH FORCE ON DEMAND START WITH sysdate+0 NEXT (round(sysdate) + 1/24) + 1
i think i read it as every hour but i'm not sure
回答1:
SQL> alter session set nls_date_format = 'yyyy-mm-dd :hh24:mi:ss';
Session changed.
SQL> select sysdate from dual;
SYSDATE
--------------------
2008-12-19 :12:18:28
SQL> select (round(sysdate) + 1/24) + 1 from dual;
(ROUND(SYSDATE)+1/24
--------------------
2008-12-21 :01:00:00
回答2:
To answer your first question (will this run once an hour?):
Nope, this will run once when you create it because of this clause:
START WITH sysdate+0
Personally, I think the "+0" is extraneous, as now is now.
Then it will run tomorrow at 1 a.m., because of the following clause:
NEXT (round(sysdate) + 1/24) + 1
The "1/24" part calculates when 1 a.m. is, since Oracle dates are actually stored as numbers, with the decimal part indicating hours, minutes, etc. The syntax is just fine.
回答3:
I'm not 100% sure that it's legal in a materialized view scheduling statement, but you might like to try the (arguably) more intuitive INTERVAL specification:
round(sysdate) + interval '1 1' day to hour
Other examples here: http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/sql_elements003.htm#SQLRF00221
回答4:
i think using
NEXT (trunc(sysdate) + 1/24) + 1
is more accurate
来源：https://stackoverflow.com/questions/380694/oracle-materialized-view-refresh-time