I thought it was pretty clear.  But it's always possible to find a better way to explain it.  I got a bit lost at the point I talked about a circular reference.  That could have been better.  But I guess an explanation that didn't have a 100% perfect explanation is better than no show at all.  

I did this show in response to a real-world discussion.  I'll not bother with any more about RDBMS matters.
