I have 2 separate queries, which effectively are the same except they
draw data from separate tables. Both tables are (design-wise)
identical, only the data is different. for each query, there are 2
tables with a standard LEFT JOIN. One field of the query is calculated,
looking for a NULL in one table, and then using a field from the second
table in that case. One query looks like this:

PARAMETERS [Month] Text ( 255 );
SELECT GR_CUSTOMER.CST_FIRSTNAME, IIf(GR_CUSTOMER!CST_LASTNAME Is Not
Null,GR_CUSTOMER!CST_LASTNAME,GR_FAMILY!FAM_FAMILYNAME) AS LASTNAME,
GR_CUSTOMER.CST_BIRTHDATE, GR_FAMILY.FAM_ADDRESS1,
GR_FAMILY.FAM_ADDRESS2, GR_FAMILY.FAM_CITY, GR_FAMILY.FAM_STATE,
GR_FAMILY.FAM_ZIPCODE
FROM GR_CUSTOMER INNER JOIN GR_FAMILY ON GR_CUSTOMER.FAMILY_ID =
GR_FAMILY.FAMILY_ID
WHERE (((MonthName(DatePart("m",[CST_BIRTHDATE]),1))=[Month]));

We'll call this query QUERY1. This query executes PERFECTLY. The second
query (we'll call it QUERY2) is identical, except for substituting the
tables names where appropriate.

However, when I try to creat a UNION query, like
Table QUERY1 UNION Table QUERY2

the calculated field, "LASTNAME", is EMPTY!

I have attempted to use the Nz() function in place of the IIF()
statement (it behaves the same way). If I use any other non-calculated
field for the ALIAS field "LASTNAME", the full UNION query works fine
as well!

Any thoughts as to what might cause such a problem with the ALIAS on a
calculated field?

Thanks in advance,
Mike