[rt-users] referencing user custom fields in TicketSQL?

[Mark D. Nagel]

Is there any way to reference a user's custom fields via TicketSQL?   
The reason for wanting this is for running ticket reports based on those 
fields, e.g., show tickets opened by all users with a particular custom 
field value, etc.  Seems like it should a simple thing to do, but I have 
looked in the list archives and wiki, and I have not found anything yet. 
If anyone has any pointers, I'd appreciate it.

Thank you,
Mark