Avoid UNION Function

To optimize the efficiency of the underlying SQL query, best practice is to avoid using the UNION function in queries. The Access SQL Portal query is created to use on a repeated basis, so take the extra development time to ensure the underlying SQL is as efficient as possible. The UNION function essentially doubles the latency of a SQL query for each time it is used as it results in executing multiple SELECT statements within one query. While UNION is not forbidden and is sometimes necessary, make a reasonable effort to develop a SQL query that keeps UNION to a minimum.