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Chapter 3. Working with Multiple-Table Queries > Creating a Unique Values Query

Creating a Unique Values Query

Most business data—dealing as it does with unique customers, suppliers, products, shippers, and employees—is stored in tables that are designed to prevent duplicate records. In most cases, preventing duplicates is a straightforward matter of adding a primary key field (such as a customer account number or employee ID number), which, by definition, does not allow duplicate values. You can also add an index to any field and specify the Yes (No Duplicates) option in the table design window's Indexed property.

However, some tables are set up to allow duplicate values. For example, consider a simple table that contains only employee names and the dates on which they took customer orders. A single employee can take more than one order on a given day, so that table will have multiple records with the same data.


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