On Thu, Apr 3, 2014 at 6:32 PM, Roman Fleysher < roman.fleys...@einstein.yu.edu> wrote:
> Dear SQLiters, > > Could some help if this is bad design or my lack of knowledge of SQL: > > I have a table that keeps track of bad metrics from exams: > > badMetric(examID, metric, reason) > > I want to filter-out bad ones and keep only good ones from the user > request: > > request(examID, metric). > SELECT eximID, metric FROM request EXCEPT SELECT eximID, metric FROM badMetric; > > I thought: > > SELECT request.examID, request.metric FROM request, badMetric > WHERE NOT (request.examID = badMetric.examID AND request.metric = > badMetric.metric) > > This produces empty list. Is it because the badMetric is actually empty > and "FROM request, badMetric" produces cross product of not-empty with > empty tables which is an empty table? > > Is this a bad design and I should add a quality column: > > badMetric(examID, metric, reason, quality) > > What could be other solutions? > > Thank you, > > > Roman > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
