text: --test update(nvarchar) for list partition(have NULL value) with null value.
  create table list_test(id int not null ,
  				test_char char(50),
  				test_varchar varchar(2000),
  				test_bit bit(16),
  				test_varbit bit varying(20),
  				test_nchar nchar(50),
  				test_nvarchar nchar varying(2000),
  				test_string string,
  				test_datetime timestamp,
                                  primary key (id, test_nvarchar))
  	PARTITION BY LIST (test_nvarchar) (
  	    PARTITION p0 VALUES IN (N'aaa',NULL,N'bbb',N'ddd')
  	);
  	insert into list_test values(1,'aaa','aaa',B'1',B'1011',N'aaa',N'aaa','aaaaaaaaaa','2006-03-01 09:00:00');
  	insert into list_test values(2,'bbb','bbb',B'10',B'1100',N'bbb',N'bbb','bbbbbbbbbb','2006-03-01 09:00:00');
  	insert into list_test values(3,'ddd','ddd',B'100',B'1110',N'ddd',N'ddd','dddddddddd','2006-03-01 09:00:00');
  	insert into list_test values(4,'aaa','aaa',B'100',B'1110',N'aaa',N'aaa','aaaaaaaaaa','2006-03-01 09:00:00');
  	insert into list_test values(5,'bbb','bbb',B'100',B'1110',N'bbb',N'bbb','bbbbbbbbbb','2006-03-01 09:00:00');
  	insert into list_test values(6,'ddd','ddd',B'100',B'1110',N'ddd',N'ddd','dddddddddd','2006-03-01 09:00:00');
  	insert into list_test values(7,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'2006-03-01 09:00:00');
  update list_test set test_nvarchar     = NULL where  test_nvarchar     = N'aaa';
  
  select * from list_test order by id;
  
  
  drop table list_test;
  