- From: Peter Wilson <pwilson@gorge.net>
- Date: Thu, 21 Apr 2005 16:25:49 -0700
- To: public-rdf-dawg-comments@w3.org
A suggestion: SQL databases often contain a WITH TIES, or TOP clause. This works like LIMIT but interacts with the sort criteria so that equal keys are also included at the cutoff point. This option only makes sense when orderby is specified. E.g. SELECT ?Salesman, ?Revenue FROM ... WHERE ... ORDER BY ?Revenue DESC LIMIT 5 WITH TIES The following: S1 10,000 S2 20,000 S3 22,000 S4 25,000 S5 19,000 S6 10,000 S7 5,000 Would produce six results due to ties in the 5th place: S4 25,000 S3 22,000 S2 20,000 S5 19,000 S6 10,000 S1 10,000 Note that this does not permit any control of the ordering of S6 and S1. A more flexible scheme is possible: SELECT ?Salesman, ?Revenue FROM ... WHERE ... ORDER BY ?Salesman // The final ordering of the result LIMIT 5 BY ?Revenue DESC // The ordering used to select the LIMIT candidates. Of course this involves a double sort - typically the second sort is small. This is implemented as the TOP clause in MS Access and SQL Server. The lack of the second syntax form is often a problem in applications.
Received on Thursday, 21 April 2005 23:29:56 UTC