UNION

UNION is a select statement
Used to combine records from two queries while excluding any duplicates.
When you compare 2 tables both tables must have the same number of fields, but the fields do not have to have the same data type.

(Query > SQL Specific > Union)

The only way to work with a union query is in the SQL view

SELECT       LastName 
             Firstname 
FROM         TableName1 
UNION 
SELECT       LastName 
             Firstname 
FROM         TableName2 

SELECT       * 
FROM         CUSTOMERS 
UNION 
SELECT       * 
FROM         CUSTOMERS 

UNION ALL

Used to combine records from two queries while including any duplicates