The purpose of the SQL UNION query is to combine the results of two or more queries into a single result set. The list contains all the rows belonging to all the queries in the union. This applies to queries in SQL Server or Microsoft Access. A common question is whether to use the UNION or UNION ALL syntax.
The main difference between UNION ALL and UNION is that, UNION only selects distinct values and sorts the results, while UNION ALL selects all values (including duplicates) without sorting. Read our revised paper on UNION versus UNION ALL SQL Syntax to learn more about the differences, see some examples, and understand why you would use one versus the other.
For more tips and using queries, visit our Microsoft Access Query Help Center.