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 >>>>> >> >> > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
