You can build queries on Excel files.
If you're working in the Web Client, make sure the Excel file you want to use as a data source is available in the SAP BI Platform Repository, in Google Drive, or in Microsoft OneDrive (including SharePoint Online). Only the Rich Client supports files stored locally.
The Data Source dialog box contains a category SAP BI Platform Repository, with Excel.

When you build a new query and the data source you use is an Excel file you have various options to browse the SAP BI Platform Repository such as Categories, Favorites, and so on.
In the Excel Data Provider dialog box, you may define the properties to interpret the Excel file.

The Query Panel which has got the same look no matter the data source you use, is displayed.

Select the objects to query or to use in filters. When your query is complete, click Run.