When
a hash object has multiple values for a single key, you can use
the DO_OVER method in an iterative DO loop to traverse the duplicate
keys. The DO_OVER method reads the key on the first method call and
continues to traverse the duplicate key list until the key reaches
the end.
If you switch the key
in the middle of an iteration, you must use the RESET_DUP method to
reset the pointer to the beginning of the list. Otherwise, SAS continues
to use the first key.