求一条查询语句

Question

select * from yourtable a where rid<>0 and (select sum([len]) from yourtable where rid<>0 and rid<=a.rid)<200

Answer 1

有点不太理解这句：[LEN]累加小于200.0的最大的[RID]值？
照我现在的理解试了一下
SELECT max(a.rid)
FROM PIPES a
WHERE (RID <> 0) AND
          ((SELECT SUM([len])
          FROM PIPES
          WHERE rid <> 0 AND rid <= a.rid) < 200)

Answer 2

select * from PIPES where [RID] = (select Max([RID]) from PIPES where [RID]<>0 and sum([len]) <200 group by [RID] )

Answer 3

这是数据
CID         RID         LEN                      
----------- ----------- ------------------------ 
1           1           0.0
2           0           10.232206
3           0           10.250839
4           0           10.269472
5           0           10.288105
6           0           10.306738
7           0           10.325371
8           0           10.344005
9           0           10.362638
10          0           10.38127
11          2           10.38127
12          0           10.399903
13          0           10.418536
14          3           10.418536
15          4           10.418536
16          0           10.437169
17          0           10.455802
18          0           10.474435
19          0           10.493068
20          5           9.5117006
21          6           9.5303335
22          7           9.5489664
23          8           9.5676003
24          9           9.5862331
25          10          9.604866
26          11          9.6234989
27          12          9.6421318
28          13          9.6607647
29          14          9.6793976
30          15          9.6980305
31          16          9.7166634
32          17          9.7352962
33          18          9.7539291
34          19          9.772563
35          20          9.7911959
36          21          9.8098288
37          22          9.8284616
38          23          9.8470945
39          24          9.8657274
40          25          9.8843603
41          26          9.9029932
42          27          9.9216261
43          28          9.940259
44          29          9.9588919
45          30          9.9775248
46          31          9.9961586
47          0           10.014791
48          0           10.033424
49          0           10.052057
50          0           10.07069要求结果
[RID]
----------------
21

Answer 4

根据我给的数据， wanyingsong(豌豆) superren() 都能够得出正确结果，谢谢两位，恐龙兄的好像不行。给分，结贴。