One order can become several report rows.

A fictional example

Order O-47 has a total of 300 and two line items. A combined list can contain two rows for that order. Summing the repeated order total gives 600 even though only 300 was ordered.

Decide whether the measure belongs to the order or the line item, then calculate at the correct level. A chart can look plausible while repeating the wrong value.

Use stable identifiers.

A customer name may change or be shared. Keep a dependable record identifier and a mapping to the source where data is imported. Review unmatched and duplicate relationships explicitly.

Preserve useful history.

Agree whether a report needs current status or the status at a past date. Overwriting today's field does not automatically preserve the information needed for a historical measure.

Check with known records.

Use a small fictional set with ordinary and exceptional cases. Compare record counts, totals and the route back to supporting details before trusting a larger dashboard.