For a drill link from a column header, which requirement must be met regarding the data columns?

The correct requirement is that there must be at least two visible data columns for a drill link from a column header. This is essential because the functionality of drill links is designed to provide more detailed information by navigating through a hierarchy of data. If only one visible data column were present, it would not provide sufficient context or comparison for users to effectively drill down into the data.

Having multiple visible data columns allows users to see related metrics side-by-side, enriching the analysis and facilitating a better understanding of the data relationships. For example, with two or more data columns, a user can investigate trends across different metrics, identify patterns, and derive insights that are essential for informed decision-making.

The requirement for multiple visible columns is foundational to the interaction mechanics of drill links, ensuring that users have the necessary data to perform meaningful analysis rather than just looking at isolated data points.