RE: How to transform flat structure into hierarchical one?

["Paulo Gaspar" <paulo.gaspar@xxxxxxxxxxxx>]

I am still a bit confused, but interested too.

ADO does not do it in ONE round trip. But it does 
not use nested cursors either.

In the relation-based shape hierarchies ADO executes
one round trip per SQL statement in the "SHAPE".

Example: if one defines a relation-based SHAPE to 
return authors and (respective) books - to use a M$ 
classic - ADO's Shape Provider will execute 2 SQL
statements:
 - 1 to return all the authors;
 - 1 to return all the books.
Then it will build the nested recordset structure in
memory.

2 round trips even if there are 200 authors.
NO nested cursors.


But you are talking about views. On the server layer?

I am interested in understanding that, since it could 
often be a more efficient way of obtaining nested XML
than ADO.


The point is: when one can not efficiently define all
the records necessary for each level of the SHAPE, it
means that the only option is to parameterise the SQL
statement to obtain each nested recordset depending
on each record of its master recordset.

ADO supports this trough "parameterised hierarchy" 
SHAPE. In this case, for the example above (with 200
authors), 201 round trips would be necessary:
 - 1 to return all the authors;
 - 1 per author to return all his/her books.

This might be worse than a nested server cursor.


I have both alternatives. I am starting to use Oracle
and I am using ADO with it. But the nested views you
are talking about sound interesting for those 
difficult cases.

So... in which layer do those nested cursors work in
Oracle? 
Database? OAS?

Thank you very and have fun,

Paulo
(paulo.gaspar@xxxxxxxxxxxx)

P.S.: I hope this is not considered (totally) off 
topic. This just has to do with the most efficient 
way to build data hierarchies in that cycle we keep 
dealing with:
(DB)data -> XML -> XSL -> HTML/OtherOutput



> -----Original Message-----
> From: owner-xsl-list@xxxxxxxxxxxxxxxx
> [mailto:owner-xsl-list@xxxxxxxxxxxxxxxx]On Behalf Of Steve Muench
> Sent: Saturday, June 10, 2000 07:04
> To: xsl-list@xxxxxxxxxxxxxxxx
> Subject: Re: How to transform flat structure into hierarchical one?
> 
> 
> Using our object view technology, you can define a
> view with nested structure as you have illustrated
> with ADO and retrieve the entire nested structure in a 
> single round trip. It was just the nested CURSOR() 
> function to which I was referring that will need
> additional roundtrips.
> 
> Thanks for the correction on ADO.
> 
> ______________________________________________________________
> Steve Muench, Lead XML Evangelist & Consulting Product Manager
> Business Components for Java & XSQL Servlet Development Teams
> Oracle Rep to the W3C XSL Working Group
> Author "Building Oracle XML Applications", O'Reilly, Oct 2000
> 
> 
>  XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list
> 


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list