SQL insert in rlm_expr

I am fairly new to Radius, so please forgive me if this question is very basic. I am using version 3.0.14 and I know you can use the sql module in rlm_expr e.g %{sql:SELECT.....WHERE...} Now I am wondering if this is limited to select statements only or can I insert a row into a custom table like this: %{sql:INSERT INTO mytab (id) values (100)} I tried this in a policy and the policy executes fine (debugging shows that it is executing the insert) and returns ok, but the mytab table stays empty. Am I doing something wrong or is it just not supported? Thanks! Koos