I've not tried this.. and I know that @DbColumn may NOT return an array but from a Formula language perspective this may work.  Not sure if you have to check for error on @DbLookup either.  There is a [FAILSILENT] option in formula language.

var customers = @Sort(@DbColumn(new Array("s1","SO1.nsf"),"notices",10):@DbLookup(new Array("s1","SO2.nsf"),"allnews","Yes",6));

My understanding is that the @DBColumn and @DBLookup are not very efficient. I had a situation where I was getting a returned document collection from a FTIndex search but then needed to sort it into a sequence that was fed into a repeat control. As the result of the search could be several hundred documents I found the using other methods very cumbersome and slow. I changed it to using the treeMap and the result was a quick clean solution. 

I have used the treeMap in several different situations where what I wanted was a unique sorted list of values.

Here is a link to how this ended up:

http://www-10.lotus.com/ldd/xpagesforum.nsf/xpTopicThread.xsp?documentId=43F21C163B41891A85257BE800728E66#247FE3C55D48015B85257BE9006C2BD9

I got the TreeMap to work and it does a great job sorting by date.  However, I cannot use this method because it omits duplicates.  So, if I have two dates that are the same, it only uses one entry with that date and doesn't display the other.  Any other ideas how I can get a table to sort in xpages by date?