Short cut problem? Can it be implemented by using PL/SQL?

Question

I am an oracle fan from China. This is the first message I published on the forum. Thanks your kindness.
Now, We are faced with a problem of the shortest roadsect problem. The table has such columns:
startcrossingid, endcrossingid, roadsectid, roadsectlength
1 2 1 100
1 3 2 90
1 4 3 80
2 5 4 70
3 5 5 85
4 5 6 95
Column startcrossingid means the start point of a roadsect. column endcrossingid means the end point of a roadsect. column roadsectid means a roadsect.
column roadsectlength means the length of a roadsect.
We want to implement it by using PL/SQL, such as by
a stored procedure. I am trying to find the solution.
If you have some usful suggestion or code, please give
me some help. Any suggestion is very thankful!
Xiexie!

Answer 1

Hi,
Good challenge, try it for sortest way from 1 to 5 :
SQL> select * from road;
STARTCROSSINGID ENDCROSSINGID ROADSECTID ROADSECTLENGTH
              1             2          1            100
              1             3          2             90
              1             4          3             80
              2             5          4             70
              3             5          5             85
              4             5          6             95
              5             6          7              5
7 rows selected.
SQL> select x.roadsectid
  2  from ------------------------------------
  3  (select *
  4  from
  5  (select abs(num1-num2) as path,b.*
  6  from (select level as num1,rownum as num2,a.*
  7        from road a
  8        where ENDCROSSINGID<=5
  9        and    STARTCROSSINGID>=1
10        connect by prior ENDCROSSINGID=STARTCROSSINGID) b) c) x,---------------------------------
11  (select d.path, min(d.lengthroad) as lengthroad
12  from
13  (select path,sum(ROADSECTLENGTH) as lengthroad
14  from
15  (select abs(num1-num2) as path,b.*
16  from (select level as num1,rownum as num2,a.*
17        from road a
18        where ENDCROSSINGID<=5
19        and    STARTCROSSINGID>=1
20        connect by prior ENDCROSSINGID=STARTCROSSINGID) b) c
21  group by path) d,
22  (select abs(num1-num2) as path,b.*
23  from (select level as num1,rownum as num2,a.*
24        from road a
25        where ENDCROSSINGID<=5
26        and    STARTCROSSINGID>=1
27        connect by prior ENDCROSSINGID=STARTCROSSINGID) b) e,
28  (select abs(num1-num2) as path,b.*
29  from (select level as num1,rownum as num2,a.*
30        from road a
31        where ENDCROSSINGID<=5
32        and    STARTCROSSINGID>=1
33        connect by prior ENDCROSSINGID=STARTCROSSINGID) b) f
34  where d.path=e.path
35  and e.STARTCROSSINGID=1
36  and  d.path=f.path
37  and f.ENDCROSSINGID=5
38  group by d.path) y,----------------------------------------------------------
39  (select min(d.lengthroad) as lengthroad
40  from
41  (select path,sum(ROADSECTLENGTH) as lengthroad
42  from
43  (select abs(num1-num2) as path,b.*
44  from (select level as num1,rownum as num2,a.*
45        from road a
46        where ENDCROSSINGID<=5
47        and    STARTCROSSINGID>=1
48        connect by prior ENDCROSSINGID=STARTCROSSINGID) b) c
49  group by path) d,
50  (select abs(num1-num2) as path,b.*
51  from (select level as num1,rownum as num2,a.*
52        from road a
53        where ENDCROSSINGID<=5
54        and    STARTCROSSINGID>=1
55        connect by prior ENDCROSSINGID=STARTCROSSINGID) b) e,
56  (select abs(num1-num2) as path,b.*
57  from (select level as num1,rownum as num2,a.*
58        from road a
59        where ENDCROSSINGID<=5
60        and    STARTCROSSINGID>=1
61        connect by prior ENDCROSSINGID=STARTCROSSINGID) b) f
62  where d.path=e.path
63  and e.STARTCROSSINGID=1
64  and  d.path=f.path
65  and f.ENDCROSSINGID=5) z----------------------------------------------------------
66  where x.path=y.path
67  and   y.lengthroad=z.lengthroad;
ROADSECTID
         1
         4
SQL> Replace 1 and 5 by parameters...
Good luck
Nicolas.