Some columns in a list often contain data that in some way is hierarchically superordinate to values in other columns.
Example
The Airline Carrier column contains the names of the airline carriers All other columns contain data that describes the flights of each airline in detail, for example, flight number, flight date, price, and so on. You can therefore view the Airline column as superordinate to the other columns.
You can highlight the hierarchical structure within a list by displaying the list as a hierarchy.
For more information: Showing and Hiding Hierarchies.
The following list outlines the most important properties of a hierarchy:
The hierarchically superordinate columns are called hierarchy columns. You can set any number of columns as hierarchy columns. All hierarchy columns are then merged into one column and displayed in the first column of the list.
Sorting
The list is automatically sorted according to all hierarchy columns. You can change the sort direction and sort sequence.
For more information: Sorting for Multiple Columns
Showing and hiding hierarchy levels
The data that is hierarchically subordinate can be hidden or shown.