If Uniform has a given EmployeeName twice, you will get the Employee.Name twice in this query. Thus it would be a different result than if you did not join with Uniform.
David ________________________________ From: Charles Samuels <char...@cariden.com> To: General Discussion of SQLite Database <sqlite-users@sqlite.org> Sent: Tuesday, May 29, 2012 8:21 PM Subject: [sqlite] Why can't sqlite disregard unused outer joins? Suppose you have a query like this: select Employee.name from Employees left join Uniform on (EmployeeSize.name=Uniform.employeeName) This query's result should be identical weather or not we have that join; it's an outer join, not an inner join, afterall. However, explain query plan (and my time measurements) seem to indicate that the the query with the join is far slower/more complex. Is it hypothetically possible that the optimizer could avoid the join? Is there a way to get sqlite to do so? Is this a planned feature? Why do I ask? I have a big view that joins a whole bunch of a tables (including with a virtual table), but most queries use only a subset of those queries actual data and I'd rather not get hit by that performance penalty. Since my queries come from the user, I don't want to have them do the joins on their own, it'd be tedious. Charles _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
