mysql> use radius

Reading table information for completion of table and column names

You can turn off this feature to get a quicker startup with -A

Database changed

mysql> delete FROM `radacct` WHERE `acctstarttime`<'2016-12-31 23:59:59';

Query OK, 69242 rows affected (27.72 sec)

======= if table data full =====

use radius

truncate table radacct;