Unions and Grouping

I have a question about the SQL Specifications in regards to Unions...

I recently put together a query that involved unions similar to the
following:

SELECT
'Query 1' as id,
my_value
FROM my_view
UNION
SELECT
'Query 2' as id,
my_value
FROM my_other_view
;

The first query in the union gave me 39 records and the second gave me 34
records. I was expecting the union to give me 39 + 34 = 73 records.

When I ran this against DB2, I got 35 records (not sure about PostgreSQL -
will have to try it when I get home). What I found was when I did a group
by my_value on each query I got two values that then added to 35. The
reason was, my_value was duplicated in my_view and in my_other_view. What
the Union appeared to be doing was to gather the data and then do a group by
on the complete results. I expected it to only eliminate duplicates BETWEEN
the two queries, not WITHIN the queries.

My question, what do the SQL Specifications say should happen on a Union?
Is it supposed to eliminate duplicates even WITHIN the individual queries
that are being unioned?

Thanks!

--
==================================================================
Aaron Bono
Aranya Software Technologies, Inc.
http://www.aranya.com
http://codeelixir.com
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