Currency conversion table is used for automatic conversion of money fields in Datamart.
Once the Datamart is set up, the exchange rates will be applied automatically. See How to Set up Currency Conversion in Datamart.
The exchange rates are looked up at the query time, meaning there is no need to refresh Datamart after updating exchange rates.
The conversion rates needed for pricing purposes usually do not change every day, typically they remain valid for a week or a month. The currency conversions can be specified either per day, or per date range.
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