https://ivanluminaria.com/en/tags/hierarchies/Recent content in Hierarchies on Ivan LuminariaHugoenTue, 20 Jan 2026 08:03:00 +0100https://ivanluminaria.com/en/posts/data-warehouse/ragged-hierarchies/Tue, 20 Jan 2026 08:03:00 +0100https://ivanluminaria.com/en/posts/data-warehouse/ragged-hierarchies/<p>Three levels. Top Group, Group, Client. It looks like a trivial structure — the kind of hierarchy you draw on a whiteboard in five minutes and that any BI tool should handle without issues.</p> <p>Then you discover that not all clients belong to a group. And that not all groups belong to a top group. And that the aggregation reports the business asks for — revenue by top group, client count by group, <span class="glossary-tip" tabindex="0" data-glossary-desc="Navigation in reports from an aggregated level to a detail level, typical of OLAP analysis and data warehouses." data-glossary-url="https://ivanluminaria.com/en/glossary/drill-down/" data-glossary-more="Read more →">drill-down</span> from the top to the leaf — produce wrong or incomplete results because the hierarchy has holes.</p>