Re: Dealing with RDB NULL values (was: Q: ISSUE-41 bNode semantics)

Enrico,

I'm trying to understand your proposal and comments on the wiki in order to
come up with my proposal using your same examples and queries. I do not want
to be sloppy :) ... so I'm writing the queries in SQL.

Query A: select A from R
Query B: select * from R as x, R as y where x.A = y.A

However, I'm unsure how to write Query C (it's a bit confusing using a
sparql-like graph query syntax over relational tables). As I understand this
query is to select all the rows of the table R except the rows that have a
value in the attribute A. Is this right? If so, the SQL query would be

select * from R where id not in ( select id from R where A is not null)

Thanks for your clarification. With this, I will be able to present my
proposal

Juan Sequeda
+1-575-SEQ-UEDA
www.juansequeda.com


On Thu, May 19, 2011 at 8:05 AM, Enrico Franconi <franconi@inf.unibz.it>wrote:

>
> On 19 May 2011, at 10:35, Michael Hausenblas wrote:
>
> > http://www.w3.org/2001/sw/rdb2rdf/wiki/RDBNullValues
>
> I've committed in the Winki my part of the story.
> I hope it is clearer now.
> --e.
>
>