This SQL statement is executed whenever Accounting-Request
Alive or Interim-Update message is received. It is expected to update the
details of the session in the SQL database. Special formatting characters
may be used (the %{attribute} ones are probably the most useful). %1 by
the NAS IP address, %2 by the NAS-Port, %3 by the SQL quoted
Acct-Session-Id. If UpdateQuery is defined as an empty string, then the
query will not be executed and ReplaceQuery, if defined, or AddQuery
otherwise, will be used. The default is the empty string.