If the Join tool is duplicating rows, it usually means the key you're joining on isn’t unique, so Alteryx is creating every possible match. For a simple “show me where these two columns differ” check, the Formula or Filter tool is often easier.
Something like a basic expression — {Column1} != {Column2} — will instantly give you only the mismatches without any duplication. Much cleaner than trying to force it through a Join.
