This optional parameter allows you to define a custom SQL
query to deallocate all previously allocated addresses for a NAS. If the
DeallocateByNASQuery is an empty string or not defined, no deallocation
query is executed. This query is not defined by default currently. %0 is
replaced by the SQL quoted NasId.
# Process Accounting-On and Accounting-Off
DeallocateByNASQuery update RADPOOL set STATE=0, TIME_STAMP=%t where NAS_ID=%0