Hi, Hi, I remember having had such a discussion with Hugo and matthias when choosing what could be the best way for doing aggregates and relational queries in QGIS.
At that time, we chose to test virtual layers path because all database query planner stuff seemed too much work to recode in QGIS core, and because demand from French ministry was to allow users to do advanced relational queries without having a full DB (many users are not granted to do that in by organisations). Anyway, I agree with Paolo that query layers certainly are for advanced SQL users, and are clearly not a straightfull path just to compute a max value in an expression engine.. I have two concerns: 1 - Having aggregate functions in expressions would be very handy. What I fear is that having expressions syntaxes between two worlds could be strange for new comers. "CASE WHEN" instead of "if(condition, value)" but aggregate expression instead of GROUP BY... Don't you feel so? Should we offer both syntax for SQL fans and spreadsheet fans (with some info in documentation panel pointing that both expressions are equivalent) ? Anyway, any of the two syntaxes wil still be clearer than having to put a VB code bloc like in Arcgis :) 2 -Question for the future: Is aggregates with expression the beginning of a relational engine in QGIS? If yes, what should be the future for virtual layers? Still use SQLITE with its pros and cons, or switch to a pure core API (less caveats, but lot of work for sure)? Thoughts? Cheers Régis -- View this message in context: http://osgeo-org.1560.x6.nabble.com/Aggregates-within-expression-engine-tp5256639p5257591.html Sent from the Quantum GIS - Developer mailing list archive at Nabble.com. _______________________________________________ Qgis-developer mailing list [email protected] List info: http://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-developer
