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The UNION ALL operator to include duplicate records

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This article is from the book "Access 2007 Pure SQL

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The UNION ALL operator

Combine customer records from two data sources and allow duplicates to appear

Discussion:

The UNION operator will exclude duplicate records.  Suppose we want to combine two lists, but we also want to include duplicates.  For this purpose, we need to use the UNION ALL operator.  Have a look at the number of records returned.  In this case, it should be 201 + 20 for a total of 221, and this is exactly what we get.  (Remember that we have 201 records in the customer table and 20 in the tbls_customers_un). 

Code:

SELECT lastname, firstname, city, state, zip

FROM customers

UNION ALL

SELECT lastname, firstname, city, state, zip

FROM tbls_customers_un
 

Result: