Naz,
>The ability to manipulate trees with single queries
>was what made them so scalable in my mind. What is
>the better way to handle large frequently updated trees?
>This is the best method I know, I'd love to
>learn of a better one.
For large frequently updated trees & DAGs I prefer edge lists, examples
at http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html.
PB
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Naz Gassiep wrote:
Really? The ability to manipulate trees with single queries was what
made them so scalable in my mind. What is the better way to handle large
frequently updated trees? This is the best method I know, I'd love to
learn of a better one.
- Naz.
Peter Brawley wrote:
Naz writes
The definitive answer to anything that
requires trees in SQL is nested sets.
They are not definitive when the tree is large and must be updated
frequently.
PB
-----
Naz Gassiep wrote:
The definitive answer to anything that requires trees in SQL is nested
sets. I have written a tutorial on the subject, as this is about the
most asked question in DB relational data modeling.
http://www.mrnaz.com/static/articles/trees_in_sql_tutorial/
Enjoy :)
- Naz.
Peter Brawley wrote:
tbt
the number of levels in this table is unknown and the query should work
for any number of levels
please provide a sample 'select' query in mysql
That's a graph, which is recursive, so you need an sproc. See edge
list sprocs at
http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html.
PB
-----
tbt wrote:
Hi
i have a table like this
id name parent_id
1 europe
2 spain 1
3 england 1
4 france 1
5 london 3
6 mayfair 5
7 madrid 2
in this table each destination is mapped to a parent destination
eg: mayfair is mapped to london, london is mapped to england etc.
i like to write a query to find child destinations when an id is
given for
a parent destination
eg: if 3 is the id, then the result of query should be 3,5,6
if 2 is the id, then the result should be 2,7
the number of levels in this table is unknown and the query should work
for any number of levels
please provide a sample 'select' query in mysql
