Drill-down

Drill-down is a report navigation operation that allows moving from an aggregated level to a more detailed level, descending through a hierarchy.

How it works #

In a Top Group → Group → Client hierarchy:

1. Start at the highest level: total revenue by Top Group
2. Click on a Top Group to see its Groups (first-level drill-down)
3. Click on a Group to see individual Clients (second-level drill-down)

The reverse operation — going back up from detail to aggregate — is called drill-up (or roll-up).

Requirements for correct drill-down #

To work without errors, drill-down requires:

• A complete hierarchy: no missing levels (no NULLs)
• Total consistency: the sum of values at the detail level must match the total at the higher level
• Balanced structure: all branches of the hierarchy must have the same depth

If the hierarchy is unbalanced (ragged hierarchy), drill-down produces incomplete or incorrect results. Self-parenting solves this by balancing the structure upstream.

Drill-down vs filter #

Drill-down is not a simple filter: it’s structured navigation along a predefined hierarchy. A filter shows a subset of data; a drill-down shows the next level of detail within a hierarchical context.