Mysql and LDAP authentication

Hello, We use freeradius and everything works very well. We authenticate the users with our LDAP directory and we use MySQL for only one table: radippool. Now we would like to store all our freeradius data and accounting in mysql. It seems easy but we have a small question before working on this project: is it possible to use mysql without storing our users in the database? We would like to continue to use LDAP for authentication. Jean-Marc