I found it interesting that the execution plan for the union in the question was the same as if I had done a distinct from the union all
select distinct a from
(select a from a
select a from a) b
In both cases, it did a Concatenation of the two result sets then did a Distinct Sort.
It makes perfect sense that this is how the process would work, once I looked at it, but I thought it was interesting regardless.
I'm pretty easily amused though. :w00t: