UNIQUE

Why this lesson matters: UNIQUE

Return a distinct list that stays current as source data changes. In this module, the skill supports a larger goal: Create live lists and transformation pipelines that resize automatically. The practical application is to create a live customer selector list.

=UNIQUE(Sales[Customer])

Build it step by step

Work from the business question toward the formula or tool. Keep the source data separate from the output and make every important assumption visible to the reviewer.

• Define the complete source array and the shape of the required result.
• Keep the spill range clear.
• Test the formula after adding and removing source records.

Check the result and common failure points

Check for blocked spill ranges, mismatched array sizes, empty results, and unintended duplicates. Also test a known record, a missing or blank value, and a boundary case. Confirm that ranges are the same size, units are consistent, and copied references move only where intended.

• Compare at least one result with a manual calculation or filtered source record.
• Test blanks, zeros, duplicates, errors, and the exact rule boundary.
• Reconcile row counts or totals before relying on the output.

Use the result in a decision

Create a live customer selector list. Label the output clearly, state its period and unit, and explain the action it supports. A technically correct result is only complete when another person can understand, refresh, and review it.