deriving a column from union

Howdy:

Silly question:

I am creating a table. Inside this table, I am trying to create a new
column derived from two other columns from two different tables
(by the way, both have the same name).

[example]

select a.type from dates a union select b.type from systems b;

[/example]

This LOOKS like it could work, except when I try to do it, it takes
quite a bit of time (as a matter of fact, I just cancelled it for the second
time because 20 minutes is TOO long for what I need to do).

Is there a speedier way to merge those two columns into a single
column?

Thanks!

-X