Finding Paths Between Two Nodes Using SQL Sorted by Cost

Question

Hi Gurus,
I want to find all paths from source node to target node that shall be sorted by the cost. I don't know whether it could be achieved with SQL statement. How to start with this query? The script to create the underlying tables along with the data are given below:
create table nodes ( nodeId int Primary Key, nodeName varchar(50));
create table paths ( pathId int Primary Key, fromNodeId int, toNodeId int, cost int );
insert into nodes values (1,'ISL');
insert into nodes values (2,'LHR');
insert into nodes values (3,'HYD');
insert into nodes values (4,'FSL');
insert into nodes values (5,'MUL');
insert into nodes values (6,'KHI');
insert into nodes values (7,'QT');
insert into paths values (1,1,3,20);
insert into paths values (2,1,5,10);
insert into paths values (3,1,7,80);
insert into paths values (4,2,4,10);
insert into paths values (5,3,4,40);
insert into paths values (6,3,5,20);
insert into paths values (7,3,6,10);
insert into paths values (8,6,7,30);
insert into paths values (9,6,5,30);
insert into paths values (10,6,3,10);
insert into paths values (11,7,2,20);
insert into paths values (12,5,4,40);
insert into paths values (13,5,7,40);
Suppose the source = ISL and target = QT, their are various paths from ISL to QT:
Ord# Relative Path Cost
==== ================================= =================
1. ISL -> MUL -> QT 50
2. ISL -> HYD -> KHI -> QT 60
3. ISL -> QT 80
4. ISL -> HYD -> MUL -> QT 80
5. ISL -> HYD to KHI -> MUL -> QT 100
This gives us all possible paths sorted by cost.
Any hint or help will be highly appreciated.
Thanks in advance and best regards
Bilal
Edited by: naive2Oracle on Feb 11, 2011 9:59 AM

Answer 1

I like recursive with clause B-)
col path for a30
with nodes(nodeId,nodeName) as(
select 1,'ISL' from dual union
select 2,'LHR' from dual union
select 3,'HYD' from dual union
select 4,'FSL' from dual union
select 5,'MUL' from dual union
select 6,'KHI' from dual union
select 7,'QT'  from dual),
paths(fromNodeId,toNodeId,cost) as(
select 1,3,20 from dual union
select 1,5,10 from dual union
select 1,7,80 from dual union
select 2,4,10 from dual union
select 3,4,40 from dual union
select 3,5,20 from dual union
select 3,6,10 from dual union
select 6,7,30 from dual union
select 6,5,30 from dual union
select 6,3,10 from dual union
select 7,2,20 from dual union
select 5,4,40 from dual union
select 5,7,40 from dual),
tmp(nodeName,fromNodeId,toNodeId,cost) as(
select a.nodeName,b.fromNodeId,b.toNodeId,b.cost
  from nodes a,paths b
where a.nodeId=b.fromNodeId),
rec(nodeName,path,fromNodeId,toNodeId,cost) as(
select nodeName,cast(nodeName as varchar2(40)),
fromNodeId,toNodeId,cost
  from tmp
where nodeName = 'ISL'
union all
select b.nodeName,a.path || '->' || b.nodeName,
b.fromNodeId,b.toNodeId,
a.cost+decode(b.nodeName,'QT',0,b.cost)
  from rec a,tmp b
where a.toNodeId = b.fromNodeId
   and a.nodeName !='QT')
CYCLE fromNodeId SET IsLoop TO 'Y' DEFAULT 'N'
select path,cost from rec
where IsLoop ='N'
  and nodeName ='QT'
order by cost;
PATH                    COST
ISL->MUL->QT              50
ISL->HYD->KHI->QT         60
ISL->HYD->MUL->QT         80
ISL->QT                   80
ISL->HYD->KHI->MUL->QT   100