row_number()

select *,
case when row_number() over(partition by aa order by bb)>1 then null
    else qty end
from test02


select *, row_number() over(order by aa,bb ) as '行号' from test02


select *, row_number() over(partition by aa order by bb ) as '行号' from test02

结果如下：

aa	bb	qty	无序号		aa	bb	qty	无序号		aa	bb	qty	无序号
10	100	5	5		10	100	5	1		10	100	5	1
10	100	7	NULL		10	100	7	2		10	100	7	2
10	100	8	NULL		10	100	8	3		10	100	8	3
10	200	6	NULL		10	200	6	4		10	200	6	4
10	200	3	NULL		10	200	3	5		10	200	3	5
10	300	7	NULL		10	300	7	6		10	300	7	6
11	110	8	8		11	110	8	7		11	110	8	1
11	120	9	NULL		11	120	9	8		11	120	9	2
11	120	10	NULL		11	120	10	9		11	120	10	3
12	120	5	5		12	120	5	10		12	120	5	1