Mass update dated exchange rates

When dated exchange rates are enabled in Salesforce, you can use Data Loader — a Salesforce API tool — to export the DatedConversionRate object, edit the ConversionRate values in a CSV file, and import the changes in bulk. This is faster than updating each currency individually in the user interface. 

Use Data Loader to update the Exchange Rate for existing Dated Exchange Rates

First, follow these steps to get an export of the current values. You can use the exported file to update the Exchange Rate value and import afterwards:

• Launch Data Loader
• Click Export
• Enter your Salesforce username and password. Click Log in. After your login completes successfully, click Next
• Check Show all Salesforce objects to see a complete list of objects.
• Choose DatedConversionRate.
• Click Browse... and select the location or file you want to save the exported file to and press save.
• Click Next. After the object and CSV file are initialized, click OK.
• Select the following fields to query: Id, IsoCode, ConversionRate, StartDate and NextStartDate. You can also copy and paste the below select query: 
  >  SELECT Id, IsoCode, ConversionRate, StartDate, NextStartDate FROM DatedConversionRate ORDER BY NextStartDate DESC
• Click Finish, then click Yes to confirm.
• A progress information window reports the status of the operation.
• After the operation completes, a confirmation window summarizes your results. Click View Extraction to view the CSV file, or click OK to close. 

Note: We recommend that you save a copy of this file to a safe location for backup purposes as previous conversion rates are not saved.

Once you have the extracted csv file, erase any fields and records that you don't wish to update, ensuring that you keep the ID column. Once done, save the CSV and perform an update using Data Loader.

To Update data using Data Loader: 

• Start Data Loader.
• Click Update.
• Enter your Salesforce username and password. Click Log in to log in. After your login completes successfully, click Next.
• Check Show all objects to see a complete list of objects.
• Choose 'DatedConversionRate.' from the list of objects.
• Click Browse... and select the CSV file you created.
• Click Next. After the object and CSV file are initialized, click OK.
• Map the columns on the available fields and click Next.
• For every operation, the Data Loader generates two unique CSV log files; one file name starts with “success,” while the other starts with “error.” Click Browse... to specify a directory for these files.
• Click Finish, and as the operation proceeds, a progress information window reports the status of the data movement.
• After the operation completes, a confirmation window summarizes your results. Click View Successes to view your success file, click View Errors to open your errors file, or click OK to close.