Sometimes you’d like to do aggregation where a row is included in multiple rows of the output, for example, being counted multiple times or having the value added multiple times. An example of this is hierarchical data, where you want for every row to find the count of all the children in the tree – not just immediate children but also grandchildren and their children and so on, all the way down to the leaves of the tree.
It means that a given row is counted in the result for the parent, but also counted again in the result of the grandparent, and so on. It can look similar to ...
