Union queries

[Guest]

Are union queries useful? Can it be done using other kinds of queries in two
steps?

 

[Ken Snell \(MVP\)]

Union queries are very useful. No, you cannot replicate their results using
two "steps" unless you build a table with one of those steps and then fill
that table with the results of individual queries.

 

[Guest]

Can I create union queries in design view using type of query or must it be
written in sql?

ALso, can you give me an ex. of where a union query would be needed and why
it could not be acheived with 2 queries instead?

Thanks

 

[Ken Snell \(MVP\)]

Union queries cannot be created in the "grid" design view for a query. They
must be created in SQL view.

The whole purpose of union queries is to combine the records from two or
more queries, such that you get a single query as the result. I'm not sure
how to explain it better than that. For example, suppose you have two
queries that return two fields from a single table each:

SELECT Field1, Field2
FROM Table1;

and

SELECT Field1, Field2
FROM Table2;

You can run these queries independently and get the records from the query,
but only one a time. In a union query, you can combine the two queries'
output into a single query:

SELECT Field1, Field2
FROM Table1
UNION
SELECT Field1, Field2
FROM Table2;
--

Ken Snell
<MS ACCESS MVP>