When you selected Group and Replace, split or date parse, an "Errors: 0" message briefly displayed in the notification panel.
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When searching the results of a wildcard pivot, results would show in Pivot Values but not Pivot Results if there was a case mismatch. For example, searching ID would return "Order Id" and "Customer ID" in Pivot Values, but only Customer ID in Pivot Results.
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When unioning MySQL and flat file data sources in Tableau Prep Builder, an "ERROR collation mismatch, use COLLATE statements to resolve" error occurred.