Hi Even, On Fri, 04. Dec 2015 at 14:29:47 +0100, Even Rouault wrote: > Le vendredi 04 décembre 2015 14:08:40, Paolo Cavallini a écrit : > > Hi all, > > apparently the OGR SQL dialect is different from others: > > https://hub.qgis.org/issues/7380 > > Any hope to bring them to common ground?
> I believe x = NULL is an extension of the SQL standard that may > be supported or not by the various SQL engines. > AFAIK, the SQL 92 standard only accepts the "x IS NULL" syntax. > From my tests: > > - SQLite rejects "x = NULL" syntax. Not here. SELECT 1 WHERE ''=NULL returns no rows in sqlite3 - consistent with what I found in PostgreSQL and Oracle (add "FROM dual" there). > - OGR SQL accepts it (does not error on it), but it's more in the > unspecified behaviour category and apparently doesn't behave like x IS NULL. > I guess this must be evaluated like x = '' internally. That might have been the original behaviour which caused the problem - but it seems to have changed. I found that OGR SQL (if that's still the default dialect) now behaves like the others in that regard and x=NULL is different from x IS NULL. I updated the ticket accordingly. Jürgen -- Jürgen E. Fischer norBIT GmbH Tel. +49-4931-918175-31 Dipl.-Inf. (FH) Rheinstraße 13 Fax. +49-4931-918175-50 Software Engineer D-26506 Norden http://www.norbit.de QGIS release manager (PSC) Germany IRC: jef on FreeNode
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