I recently had a problem where I was using the query builder in Power BI to extract data from all files in a folder. When some new files were added to the folder my query broke.
It turns out that the issue was with my promote headers step. Because the first file the query opened changed, the header that was promoted in the filename column was different, throwing off all my subsequent query steps. I needed a way of referencing the first column without referencing it by name. Continue reading “Referencing the first column in Power Query”