Detect Changed Values Between Two Snapshots in Power Query M

Joins two snapshots of the same table by key and flags rows where a tracked column's value has changed.

Comparing & LookupsAdvancedcomparechanged valuessnapshotaudit

Power Query M code

let
    Merged = Table.NestedJoin(CurrentTable, {"ID"}, PreviousTable, {"ID"}, "Previous", JoinKind.LeftOuter),
    Expanded = Table.ExpandTableColumn(Merged, "Previous", {"Value"}, {"PreviousValue"}),
    AddedChangedFlag = Table.AddColumn(Expanded, "HasChanged", each [Value] <> [PreviousValue], type logical)
in
    AddedChangedFlag

Notes

Replace Value with the actual column you want to track for changes between snapshots.

Requirements

Two tables sharing the same key column: a current snapshot and a previous one.

How to use this snippet

In Power BI Desktop, choose Transform data to open Power Query, then open the Advanced Editor on a query (or start from a blank query).
Paste the snippet and replace the placeholder names (tables, columns, file paths) with your own. Check the requirements above first.
Run it through the Power Query M Formatter to tidy the layout.

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