this is my query=

"SELECT i.itemid,title,SortKey from Items AS i JOIN Links AS L ON
(i.ItemID=L.ItemID) WHERE L.instructorID='12232' AND courseID='12' AND
type='Audio' order by CASE WHEN Sortkey is not null then 1 else 0 end"

My SortKey can be NULL. Here's the output I am getting:
(the || is to denote sortkey column)

37542 Tape 1 ||
37544 Tape 2 ||
37819 Symphony1 ||
37820 Symphony2 ||
37821 Symphony3 ||
37828 Symphony ||
60962 Test ||
61570 New Test Record |Africa|
61572 Test 3 |Africa 1|
63186 Music for Strings |Brazil|

I want use Sortkey when it is not null. desired output:

61570 New Test Record |Africa|
61572 Test 3 |Africa 1|
63186 Music for Strings |Brazil|
37542 Tape 1 ||
37544 Tape 2 ||
37819 Symphony1 ||
37820 Symphony2 ||
37821 Symphony3 ||
37828 Symphony ||
60962 Test ||