The AODBC back-end requires access to the ODBC interface of AllegroCL named DBI. This interface is not available in the trial version of AllegroCL
Use
(require 'aodbc-v2) (asdf:operate 'asdf:load-op 'clsql-aodbc)
to load the AODBC back-end. The database type for the AODBC back-end is :aodbc.