@Test
  public void test6() throws ParseException {
    ASTNode ast = parse(
      "MERGE INTO target USING source ON target.pk = source.pk WHEN NOT MATCHED THEN INSERT VALUES(a,(source.b + 1))");
  }
here we reverse the order of WHEN MATCHED/WHEN NOT MATCHED - should we allow it?
@throws ParseException
parser/src/test/org/apache/hadoop/hive/ql/parse/TestMergeStatement.java