Asp+Access中数据库查询有关问题，多谢
求助：Asp+Access中数据库查询问题，谢谢
ID SerID num l_number
1 111111111 10 1
2 111111111 -10 1
3 123456789 8 2
4 123456789 -8 2
5 111111111 5 3
6 111111111 -3 3
7 111111111 6 4
8 111111111 -6 4
9 111111111 7 5
10 123456789 -5 5
11 123456789 12 6
12 111111111 -1 6
13 111111111 5 7
比如Access数据库中表“a”如上，我想查询字段l_number相同，并且其对应的num字段之和>0，这样的记录总数是多少，SQL该怎样写啊？（如上表查询结果应该是：4，红色标记部分）
------解决思路----------------------
------解决思路----------------------
select l_number from (select sum(num) as snum ,l_number from a group by l_number) where snum>0
------解决思路----------------------
select sum(num) as snum ,l_number from a where sum(num)>0 group by l_number
ID SerID num l_number
1 111111111 10 1
2 111111111 -10 1
3 123456789 8 2
4 123456789 -8 2
5 111111111 5 3
6 111111111 -3 3
7 111111111 6 4
8 111111111 -6 4
9 111111111 7 5
10 123456789 -5 5
11 123456789 12 6
12 111111111 -1 6
13 111111111 5 7
比如Access数据库中表“a”如上，我想查询字段l_number相同，并且其对应的num字段之和>0，这样的记录总数是多少，SQL该怎样写啊？（如上表查询结果应该是：4，红色标记部分）
------解决思路----------------------
select l_number from (select sum(num) as snum ,l_number from a group by l_number) where snum>0
------解决思路----------------------
select l_number from (select sum(num) as snum ,l_number from a group by l_number) where snum>0
------解决思路----------------------
select sum(num) as snum ,l_number from a where sum(num)>0 group by l_number