Wildcard Union of Excel Data Sources Results in Duplicate Data

Issue

When using a Wildcard Union to union Excel files together, the resulting data is duplicated.

Environment

Tableau Desktop
Tableau Prep
Excel

Resolution

To avoid duplication, the sheet and range names can be modified to have different names and then use that sheet name or named range in the matching pattern. Named ranges can also be removed from the Excel files (Formulas > Name Manager > select Named Range to be removed > Delete).

Cause

Tableau does not differentiate between named ranges and sheet name.
This behavior is "by design". Please refer to the Online Help documentation - "Note: When working with Excel data, wildcard search includes named ranges but excludes tables found by Data Interpreter."