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
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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
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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Mogens Melander
+45 40 85 71 38
+66 870 133 224
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