如下表：
SeqNo OrderNo PO ShipDate Packing ShipMode
NULL 105800A 1591872 2010-12-15 bul By Sea
NULL 105800A 2587254 2010-12-8 pre By Sea
NULL 105800A 2587254 2010-12-8 bul By Sea
NULL 105800A 2587256 2010-12-8 bul By Sea
NULL 105800A 2587256 2010-12-8 pre By Sea
NULL 105800A 2589381 2010-12-8 gbu By Air
NULL 105800A 2589836 2010-12-8 gbu By Air
NULL 105800A 2590725 2010-11-24 bul By Air
NULL 105800A 2590725 2010-12-1 bul By Air
NULL 105800A 2590725 2010-12-1 bul By Sea
希望达到如下要求：
同一个OrderNo,PO之下，如果ShipDate有几个的话，按照时间排序，Packing是pre优先于bul，ShipMode是By Air的优先于By Sea，更新SeqNo列，这里是Int类型。
到了第二个ShipDate，仍然是刚才的规则，更新SeqNo列，不过数值要比上一个ShipDate大一。比如：
SeqNo OrderNo PO ShipDate Packing ShipMode
1 105800A 1591872 2010-12-15 bul By Sea
1 105800A 2587254 2010-12-8 pre By Sea
2 105800A 2587254 2010-12-8 bul By Sea
2 105800A 2587256 2010-12-8 bul By Sea
1 105800A 2587256 2010-12-8 pre By Sea
1 105800A 2589381 2010-12-8 gbu By Air
1 105800A 2589836 2010-12-8 gbu By Air
1 105800A 2590725 2010-11-24 bul By Air
2 105800A 2590725 2010-12-1 bul By Air
3 105800A 2590725 2010-12-1 bul By Sea
请各位不吝赐教，SQL2000,拜托了！
------解决方案--------------------
declare @a table(SeqNo int,OrderNo varchar(20),PO int,ShipDate datetime,Packing varchar(20),ShipMode varchar(20))
insert @a select NULL,'105800A',1591872,'2010-12-15','bul','By Sea'
union all select NULL,'105800A',2587254,'2010-12-8','pre','By Sea'
union all select NULL,'105800A',2587254,'2010-12-8','bul','By Sea'
union all select NULL,'105800A',2587256,'2010-12-8','bul','By Sea'
union all select NULL,'105800A',2587256,'2010-12-8','pre','By Sea'
union all select NULL,'105800A',2589381,'2010-12-8','gbu','By Air'
union all select NULL,'105800A',2589836,'2010-12-8','gbu','By Air'
union all select NULL,'105800A',2590725,'2010-11-24','bul','By Air'
union all select NULL,'105800A',2590725,'2010-12-1','bul','By Air'
union all select NULL,'105800A',2590725,'2010-12-1','bul','By Sea'
SELECT SeqNo=(SELECT COUNT(1)+1 FROM @a WHERE OrderNo=a.OrderNo AND PO=a.PO AND (ShipDate<a.ShipDate OR (ShipDate=a.ShipDate AND Packing>a.Packing)
OR (ShipDate=a.ShipDate AND Packing=a.Packing AND ShipMode<a.ShipMode))
),* FROM @a a
ORDER BY OrderNo,PO,ShipDate,1