merging sequences

Hi List.
I have the two following sequences
N112 N100 N107 P2010 N109 P2014 P2015 N108 N203 N206 N307 N311
And
N112 N100 P2014 P2015 N108 N203 N306 N206 N307 N311

These are extracted from a sub tree (thus they have child and attributes). The
sequences themselves are made using the name() function, thus are sequences of
strings.
I would like to align these so that the resulting sequence contains all items,
but keeping the order, thus


N112 N100 N107 P2010 N109 P2014 P2015 N108 N203      N206 N307 N311
N112 N100                 P2014 P2015 N108 N203 N306 N206 N307 N311

The result being
N112 N100 N107 P2010 N109 P2014 P2015 N108 N203 N306 N206 N307 N311

Then, once I have this sequence, I can iterate over it and rebuild my sub tree
so that all child and attributes are kept (this part I have already).

Any help would be very appreciate.

Kind regards,
Fabien