SYMPTOM
When an attribute is duplicated in Strategy Developer, the resulting copy does not have any parent-child relationships defined. For example, if the 'Customer' attribute is duplicated in the Strategy Tutorial project, users will see the follow results:
Original attribute definition:

Attribute copy:

CAUSE
Strategy Developer is behaving as designed.
Separate attributes in a Strategy project should represent separate business concepts. Thus, it would be expected to relate the new attribute to a different set of attributes. The attribute copy operation does not know the other attributes to use as relationship targets, so Strategy Developer omits the relationships and leaves it to the user to establish them.
The Strategy SQL Generation Engine depends heavily on attribute relationships. Creating spurious relationships may cause incorrect SQL to be generated. Since Strategy Developer creates the attribute copy with no relationships, report SQL should not change simply by copying an attribute.
ACTION
Parent-child relationships must be defined manually after copying the attribute.