Map the columns before combining the spreadsheets.

Choose append, join or summary

Appending stacks comparable records into one table. Joining adds fields by matching an agreed key between tables. Summarizing groups records into a new level of detail. A request to merge sheets can mean any of these. Name the operation and the intended row unit before choosing a tool or copying cells.

Write the target schema in plain language

List the output fields, their types and their meaning. Product and Item may mean the same thing, or one may be a description while the other is a code. Record whether Price is per item, pack or another unit and which currency applies. Similar-looking column headings are a starting point for review, not proof of equivalence.

Map every source, including missing fields

Create one mapping row per source column. Specify the target, allowed transformation and unresolved questions. An absent field should become an agreed missing state rather than borrowing a nearby value. Add a source-file reference and original row reference where traceability is needed. Keep unknown columns in review until the owner decides whether they matter.

Source: supplier B
Source column: Item No.
Target: ProductCode
Type: text
Rule: preserve original identifier
Source column: Pack Price
Target: PrintedPrice
Question: confirm currency and pack quantity

• Download the blank column mapping worksheet (.txt)

Check the tool’s input assumptions

Microsoft's Power Query folder-combine guidance calls for consistent schemas and explains that columns are matched by name, not position. Different schemas therefore need preparation and transformation decisions first. Keep unrelated files out of a source collection intended for a combined import and preview the transformed result.

Source: Microsoft Support — Import data from a folder with multiple files (Power Query).

Validate relationships as well as row counts

For a simple append, reconcile accepted input rows with output rows and documented exclusions. For a join, inspect unmatched keys and keys that appear more than once on either side; these can change the number of resulting rows. For a summary, retain a route back to the detailed records. Do not use one counting rule for all three operations.

Deliver the mapping with the combined file

The final handoff should identify included sources, revisions, applied transformations and open questions. Keep data cleanup separate from decisions about which conflicting source is authoritative. A future source with a new column or unit should trigger review of the map before it is added. This makes the next batch a defined task instead of another manual reconstruction.

• Check the combined file before handoff