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Re: Limiting a query by setting a maximum number of distinct values for a given variable.

From: Steve Harris <steve.harris@garlik.com>
Date: Sat, 16 Oct 2010 07:32:37 +0100
Message-Id: <5E31FE36-569F-49C6-95AE-ADD11AFAB9CD@garlik.com>
Cc: Semantic Web <semantic-web@w3.org>
To: Olivier Rossel <olivier.rossel@gmail.com>
Only in SPARQL 1.1. But even there it can be tricky. You can use sub queries with limits in them, but the underpinning logic isn't necessarily what you'd expect - the sub query is executed logically "before" the outer query - so it's still quite tricky. A query to do what you want will be ludicrously verbose. 

In short: it's easier to do it at the application layer. Get all the towns, then do LIMIT 100 queries on each. 

- Steve

Sent on the move.

On 15 Oct 2010, at 21:23, Olivier Rossel <olivier.rossel@gmail.com> wrote:

> Well, let me rephrase a little bit the subject of my mail.
> I want to retrieve a set of towns, their various labels and their geolocation.
> The labels can be in english and/or spanish and/or french and/or deutsch.
> My data set contains a LOT of towns.
> So I will limit my query.
> I plan to retrieve towns data by packs of 100 towns.
> My first idea was to use the SPARQL "LIMIT" and "OFFSET" keywords.
> But I think they work at resultSet's row level, and each row of {town,
> label, longitude, latitude}
> counts for 1.
> So 100 rows of the resultSet do not correspond to data for 100 distinct towns.
> Is there a way to constrain my SPARQL queries to return all the data for the
> first 100 towns, then all the data for the second 100 towns, etc ?
> Note: oh, by the way, in my app, I use CONSTRUCT and SELECT ! I don't know if
> that is an important point. But anyway... :)
> Any help is gladly welcome.
> Thanks.
> --
> Olivier Rossel
Received on Saturday, 16 October 2010 06:33:55 UTC

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