Why won't this MERGE statement work?

Question

I am testing out a MERGE statement, which contains a subquery that will return no rows...on this condition, it should insert a record; however I get 0 records merged. Why is this?
Ultimately, the hard-coded values will actually be passed in as parameters. If those a record with those four values is not found, then it should insert.
MERGE INTO tb_slea_election_worksheet A
USING 
(SELECT i.slea_year,i.empid,i.bda_sum_sort,i.bda_dtl_sort FROM tb_slea_election_worksheet i
WHERE  slea_year = '2008'
AND empid = '6468T'
AND bda_sum_sort = '30'
AND bda_dtl_sort = '9999'
) B
ON (A.slea_year = B.slea_year
AND A.empid =B.empid
AND A.bda_sum_sort  = B.bda_sum_sort
AND A.bda_dtl_sort  = B.bda_dtl_sort) 
WHEN MATCHED THEN
  UPDATE SET A.fa_proj_exp_amt  = 888
WHEN NOT MATCHED THEN
  INSERT    (slea_year,empid,bda_sum_sort,bda_dtl_sort,act_exp_lst_yr,fa_proj_exp_amt)
  VALUES ( '2008','6468T','30','9999','0','55');

Answer 1

A merge statement is just a much more efficient way of doing something like this pl/sql block
DECLARE
   l_n NUMBER;
BEGIN
   FOR r IN (SELECT pk, col1, col2 FROM source) LOOP
      BEGIN
         SELECT 1 INTO l_n
         FROM target
         WHERE pk = r.pk;
         UPDATE target
         SET col1 = r.col1,
             col2 = r.col2
         WHERE pk = r.pk;
      EXCEPTION WHEN NO_DATA_FOUND THEN
         INSERT INTO target
         VALUES(r.pk, r.col1, r.col2);
      END;
   END LOOP;
END;So, if the select from source returns no rows, nothing is going to happen.
John