SQL server opfoerer sig UNDERLIGT

Jeg har foelgende:

BEGIN TRANSACTION
SELECT id_project, end_date frOM projects WHERE id_project > 12 AND id_project < 20 -- 1
SELECT id_project, end_date frOM projects WHERE id_project > 12 AND id_project < 16 -- test
UPDATE projects SET end_date = null WHERE id_project < 16
SELECT id_project, end_date frOM projects WHERE id_project > 12 AND id_project < 20 -- 2
ROLLBACK

Dette er resultatet:

1)

19    2003-08-19 11:44:43.000
18    NULL
17    2002-11-30 09:19:57.920
16    2002-06-30 09:19:58.000
15    2002-06-30 09:19:58.000
14    2002-06-30 09:19:58.000
13    2002-06-30 09:19:58.000

test)
15    2002-06-30 09:19:58.000
14    2002-06-30 09:19:58.000
13    2002-06-30 09:19:58.000

2)

19    NULL
18    NULL
17    NULL
16    2002-06-30 09:19:58.000
15    2002-06-30 09:19:58.000
14    2002-06-30 09:19:58.000
13    2002-06-30 09:19:58.000


Er der nogen der kan forklare dette? Og hvad kan jeg goere for at reperere dette?