Hi Prakash,
It's easy to make hierarchies to make drill-down operations.
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A hierarchy will be formed when you drop a field on another field.
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Deleting any member from the hierarchy would delete the actual field.
You can duplicate the field used in the hierarchy to use it as a non-hierarchial field for some calculation or visuals.
The hierarchy order can be changed as per user.
In the below image, there are not in hierarchy.
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In below image, there are in hierarchy, where - indicates the hierarchy drill up and + indicate hierarchy drill down
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Hope it helps you.