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Exported file in a spreadsheet editor
Avoiding duplicated records
It is a good practice to also include the primary key in the export definition, otherwise it can lead to duplicated records in the result of the export process. The duplicated records can occur because the dataset's columns and metric values needs to be joined and if there is no primary key, then the join is performed using all available columns. And if any of the columns contains some NULL values, the join process is not able to correctly match the records, because of the NULL values inequality.
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