Storing a linked list
Hi all,
I've got a table such as the following:
id1 char
id2 char
sample data looks like this:
id1 id2
1 3
2 4
3 5
5 6
6 8
And of course another table has something like:
id info1 info2 info3
1 blahblahblah
2 blahblahblah
I'd like to store paths to specific destinations...
In other words, the path from 1 to 8 is:
1,3,5,6,8
I was thinking of creating a table called relationships
start end path
1 8 {3,5,6}
This would allow me to easily display the path if I know the start and end, but
what it doesn't allow me to do is reuse the data.
IE: say that I calculate the path from 1 to 8 as 1,3,5,6,8, and then I want to
know the path from 3 to 6. even though this is already calculated, I have to
recalculate it as another row... hence
start end path
1 8 {3,5,6}
3 6 {5}
I considered making another table, called hops, such as:
start end relationshipID
1 8 1
table hops:
relationshipID start end
1 1 3
1 3 5
1 5 6
1 6 8
Then I could almost reuse those hops somehow but not sure.
Can anyone recommend a good way to store this data?
Thanks!
-Matt
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Re: Storing a linked list
How about:
$id1 = 1;
$id2 = 0;
while ($id1) /** or ($id2 != 8) **/
{
$sql = select * from table where id1=$id1;
$row=query($sql);
$id1=$row-id1;
$id2=$row-id2;
do_stuff();
$id1 = $id2
}
On Tue, June 19, 2007 10:58, Matt Juszczak wrote:
Hi all,
I've got a table such as the following:
id1 char
id2 char
sample data looks like this:
id1 id2
1 3
2 4
3 5
5 6
6 8
And of course another table has something like:
idinfo1 info2 info3
1 blahblahblah
2 blahblahblah
I'd like to store paths to specific destinations...
In other words, the path from 1 to 8 is:
1,3,5,6,8
I was thinking of creating a table called relationships
start end path
1 8 {3,5,6}
This would allow me to easily display the path if I know the start and
end, but
what it doesn't allow me to do is reuse the data.
IE: say that I calculate the path from 1 to 8 as 1,3,5,6,8, and then I
want to
know the path from 3 to 6. even though this is already calculated, I have
to
recalculate it as another row... hence
start end path
1 8 {3,5,6}
3 6 {5}
I considered making another table, called hops, such as:
start end relationshipID
1 8 1
table hops:
relationshipIDstart end
1 1 3
1 3 5
1 5 6
1 6 8
Then I could almost reuse those hops somehow but not sure.
Can anyone recommend a good way to store this data?
Thanks!
-Matt
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Re: Storing a linked list
Matt
I'd like to store paths to specific destinations...
See
-- Tropashko's 'materialized modell' eg
http://www.dbazine.com/oracle/or-articles/tropashko4
-- the airports example at
http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html
PB
-
Matt Juszczak wrote:
Hi all,
I've got a table such as the following:
id1 char
id2 char
sample data looks like this:
id1id2
13
24
35
56
68
And of course another table has something like:
idinfo1info2info3
1blahblahblah
2blahblahblah
I'd like to store paths to specific destinations...
In other words, the path from 1 to 8 is:
1,3,5,6,8
I was thinking of creating a table called relationships
startendpath
18{3,5,6}
This would allow me to easily display the path if I know the start and
end, but what it doesn't allow me to do is reuse the data.
IE: say that I calculate the path from 1 to 8 as 1,3,5,6,8, and then I
want to know the path from 3 to 6. even though this is already
calculated, I have to recalculate it as another row... hence
startendpath
18{3,5,6}
36{5}
I considered making another table, called hops, such as:
startendrelationshipID
181
table hops:
relationshipIDstartend
113
135
156
168
Then I could almost reuse those hops somehow but not sure.
Can anyone recommend a good way to store this data?
Thanks!
-Matt
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Re: Storing a linked list
Celko also discusses them in SQL For Smarties.
Baron
Peter Brawley wrote:
Matt
I'd like to store paths to specific destinations...
See
-- Tropashko's 'materialized modell' eg
http://www.dbazine.com/oracle/or-articles/tropashko4
-- the airports example at
http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html
PB
-
Matt Juszczak wrote:
Hi all,
I've got a table such as the following:
id1 char
id2 char
sample data looks like this:
id1id2
13
24
35
56
68
And of course another table has something like:
idinfo1info2info3
1blahblahblah
2blahblahblah
I'd like to store paths to specific destinations...
In other words, the path from 1 to 8 is:
1,3,5,6,8
I was thinking of creating a table called relationships
startendpath
18{3,5,6}
This would allow me to easily display the path if I know the start and
end, but what it doesn't allow me to do is reuse the data.
IE: say that I calculate the path from 1 to 8 as 1,3,5,6,8, and then I
want to know the path from 3 to 6. even though this is already
calculated, I have to recalculate it as another row... hence
startendpath
18{3,5,6}
36{5}
I considered making another table, called hops, such as:
startendrelationshipID
181
table hops:
relationshipIDstartend
113
135
156
168
Then I could almost reuse those hops somehow but not sure.
Can anyone recommend a good way to store this data?
Thanks!
-Matt
--
Baron Schwartz
http://www.xaprb.com/
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