An Access update can select records using one field and change another. That is useful when, for example, completed records from an approved import batch need a review flag. It also means that searching for the old flag value alone does not describe the intended scope.

Write the selection and change separately. In a fictional table, the selection might be ImportBatch B17 and Status Complete; the change might set Reviewed to Yes. Keep Pending records in that batch and Complete records in another batch as exclusion examples.

Preserve a readable SELECT version

Microsoft recommends first creating a select query that identifies the intended records, then converting it to an update query. Include the record ID, the fields used by the criteria and the field to be changed. Run the SELECT version and inspect the exact records, not only the count.

Save that selection query separately before preparing the action version. Confirm an included record and both exclusion examples. Compare the full list with the approved batch scope; ten selected rows can still be the wrong ten rows.

In Design View, Query Design, Update changes the query type and adds an Update To row. Put the new value only under the intended destination field, retaining the reviewed criteria. Microsoft warns that update-query results cannot be undone and recommends a database backup before running one.

Rehearse the effect before the live change

Use an isolated database copy for the trial, ensuring any linked tables do not still target live data. Compare the updated IDs and flags with the preserved SELECT result. Check the excluded records explicitly and verify that their values remain unchanged.

For a live operation, coordinate with the database owner so the record set does not change unnoticed between selection review and execution. Read the action confirmation against the expected scope; stop if it differs and investigate the current records.

After the authorised update, inspect the actual records again through a read-only selection. Keep the backup, criteria and accepted result together. Repeatedly running an action query is not a substitute for checking its outcome, particularly when the update expression would apply an additional change on every run.

Sources: Microsoft: Access update queries.