rlm_sql variable substitution clarification

[Guy Fraser]

I have run into an issue where we now have different types of
NAS servers. I would like to use %{Connect-Info} if available
or a string formatted from two attributes like :

D%{Ascend-Data-Rate}_X%{Ascend-Xmit-Rate}

This is how I tried to do it :

ConnectInfo_stop = \
'%{Connect-Info:-D%{Ascend-Data-Rate}_X%{Ascend-Xmit-Rate}}'

This is what I get when %{Connect-Info} is not available :

"D_X"

I haven't seen any examples where two attributes are combined 
to make one attribute.

Thanks