Mege Table Issue

Hi HasnainNB 

Here are the most common causes + fixes (in order of likelihood):

1) The other “tables” are not actually tables in Power Query

The Merge dropdown only lists queries that return a table. If a query returns a list / record / scalar / parameter, it won’t appear.

Check:

• Click each query on the left and confirm the preview shows a table with columns.
• If you see List, Record, or a single value → that query won’t show up.

Fix:

• Convert it to a table (Transform → To Table) or adjust the query to output a table.

2) Query preview is failing (so PQ can’t load candidates)

If any query has an error in preview or step evaluation, Power Query sometimes fails to populate the merge list.

Check:

• Look for queries showing Error in the preview pane or in the status bar.
• Check Applied Steps for error icons.

Fix:

• Resolve the error OR temporarily disable the failing step(s).
• Then try Merge again.

3) You’re inside a query context that limits what can be merged

Sometimes you’re editing a query that’s a function, parameter, or connection-only staging query and the merge UI behaves oddly.

Fix:

• Try merging from a “normal” query that clearly loads a table (e.g., one of your Lookup tables).
• Or duplicate the query (Right click → Duplicate) and try merging in the duplicate.

4) Privacy / firewall settings blocking combining data sources

Power Query can block combining sources depending on privacy levels (“Formula.Firewall”), and the UI can get weird.

Fix (quick test):

• File → Options and settings → Options
• Privacy: set to Ignore the Privacy Levels (temporarily, just to test)
• Or set both sources to the same privacy level (Organizational)

If it suddenly works, it’s a privacy/firewall configuration issue.

5) Power Query cache/UI glitch

This happens more than people expect.

Fix:

• Close Power Query Editor
• File → Options and settings → Options → Data Load → Clear cache
• Reopen PBIX / workbook
• Try again

Also try toggling:

• Options → Data Load → “Allow data preview to download in the background” (turn OFF, restart)

6) Data source is fine, but columns aren’t loaded yet

If the preview hasn’t fully loaded or is stalled, the merge dialog can show blank.

Fix:

1. Click Refresh Preview on the query you’re merging from.
2. Wait for preview to fully load.

Retry Merge.

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This usually happens when Power Query can’t render the preview of the second table, not because Merge itself is broken.

Most common causes (check in this order):

1. Table has an error in earlier steps
   Open the other query directly and make sure it loads rows without errors (red “Error” values).

2. The query returns zero rows at preview time
   For example:

• Filter step removes all rows

• Parameter-driven query with no default value
  Merge dropdown will appear blank if there’s nothing to preview.

1. Query depends on another query that’s disabled or broken
   If the target query references another query that fails, Merge can’t show it.

2. Data source privacy / credentials issue
   Go to Data source settings → make sure credentials are valid and privacy levels are not blocking evaluation.