<div><span class="Apple-style-span" style="font-family: tahoma, sans-serif; ">Hey James,</span></div><div><span class="Apple-style-span" style="font-family: tahoma, sans-serif; "><br></span></div><span class="Apple-style-span" style="font-family: tahoma, sans-serif; ">I think the problem might be that the query builder, when you press ok, is setting the the layer subset via QgsDataProvider::<span class="Apple-style-span" style="white-space: pre; ">setSubsetString(string). How setSubSetString works is up to the provider. In your case the provider, that you joined to, doesn't know anything about the other fields or how to filter based on them so it just returns nothing.</span></span><div>
<span class="Apple-style-span" style="font-family: tahoma, sans-serif; "><span class="Apple-style-span" style="white-space: pre; "><br></span></span></div><div><font class="Apple-style-span" face="tahoma, sans-serif"><span class="Apple-style-span" style="white-space: pre;">QGIS itself doesn't have a SQL engine in it's own right all most everything with querying, except for the basic stuff, is passed to the provider. I have had a chat to a few of the devs and it is something I am considering if and how it could be added to QGIS. Not something that I myself will be able to do, way over my head, but more just getting the ideas out there and maybe some will fund it.</span></font></div>
<div><font class="Apple-style-span" face="tahoma, sans-serif"><span class="Apple-style-span" style="white-space: pre;"><br></span></font></div><div><font class="Apple-style-span" face="tahoma, sans-serif"><span class="Apple-style-span" style="white-space: pre;">Hopefully this will at lest let you understand what is happening.</span></font></div>
<div><font class="Apple-style-span" face="tahoma, sans-serif"><span class="Apple-style-span" style="white-space: pre;"><br></span></font></div><div><font class="Apple-style-span" face="tahoma, sans-serif"><span class="Apple-style-span" style="white-space: pre;">- Nathan<br>
</span></font><br><div class="gmail_quote">On Fri, Nov 4, 2011 at 10:01 PM, James Stott <span dir="ltr"><<a href="mailto:James.Stott@npaconsult.co.uk">James.Stott@npaconsult.co.uk</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<p class="MsoNormal">I have opened an Access table via an ODBC connection. This has allowed me to open the attribute table up in QGIS. I have then done a join to join my attribute and polygon data together. I can style the data using the joined fields, and they all show up in the attribute table and the identify tool. However I cannot use these fields in a query. <u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">If I use the query builder the fields show in the fields list, and the values from the fields show in the field list. However all of my queries return no results.</p>
</blockquote></div><br></div>