>UNION does not set any relations between queries, it only combines there results. I'm not sure why you would expect anything else.
>
>>I recently crashed when I tried:
>>
>>
>>select intcolumn, charcolumn from tablea
>>union all
>>select charcolumn, intcolumn from tableb
>>The message was that the data types couldn't be converted.
>>
>>Checking SQL help, I was surprised to learn that both the number of columns and the order of the columns have to match- column names don't seem to matter at all.
>>
>>
>>So.. this UNION of all char columns doesn't crash :
>>
>>
>>select sealnumber, customer from tablea
>>union all
>>select customer,sealnumber from tableb
>>
>>but the result is whacky.
>>The sealnumber column contains sealnumbers from table A and customers from table B and
>>the customer column contains customers from table A and sealnumbers from table B

I was surprised that it ignores the column names in the second table and goes strictly by the position they occupy in the query.
I only discovered it because of my sloppy typing.
It really doesn't combine the queries in my mind now. It establishes a structure based on the first table and fits the second table into that structure based on order, regardless of columns names.
That's OK, but it's not what I expected.