Answer:

I know this wasn't the problem in this case, but I had a SIMILAR issue of "Duplicate Entry" when CREATING a composite primary key:

And the output showed just 1 row, no duplicate!

After some time I found out that if you have NULL values in these field you receive these errors. In the end the error message was kind of misleading me.

Explanation:

A primary key is a field or SET of fields with values that are unique throughout a table. Values of the key can be used to refer to entire records, because each record has a different value for the key. Each table can only have one primary key. Access can automatically create a primary key field for you when you create a table, or you can specify the fields that you want to use as the primary key. This article explains how and why to use primary keys.

To set a table’s primary key, OPEN the table in Design view. SELECT the field (or fields) that you want to use, and then on the ribbon, click Primary Key.

I think it will helpful for u..