It is often necessary to retrieve data in the data in the data, so use the following statement Select * from evenettable where eventdate> sysdate-30, when the amount of data is small, the amount of data will find the above statement Slow, but EventDate is also indexed, but why is it slower? It turned out that Oracle continued to get the changing value when it is looking for, rather than generating a conditional statement at once in our imagination and then looking for. In order to speed up the speed, we can first take the date of the day, then turn into a string, use the following sentence check, select * from eventtable where eventdate> to_date ('2001-12-1', 'YYYY-mm-dd' ). The speed is actually a few times.
