<html><head></head><body>It's called a choropleth map.<br>
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<a href="http://oobrien.com/2010/01/simple-choropleth-maps-in-quantum-gis">http://oobrien.com/2010/01/simple-choropleth-maps-in-quantum-gis</a>/ is one tutorial I found.<br>
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Jim<br><br><div class="gmail_quote">On August 1, 2016 8:07:11 PM EDT, Chuck Young <wylie1066@gmail.com> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div dir="ltr"><div><div>Thanks Jim! You are right a join! I now need to know how to get the data to show the density by varying colors depending on the density. I know it must be fairly simple bit I just don't have the key to it in my mind. Somethimes it can be rigth in front of me but I don't see it. So an example mite be good if anyone has a place in the manual or tutorial to point me to.<br /></div>Thanks again!<br /></div>Chuck<br /></div><div class="gmail_extra"><br /><div class="gmail_quote">On Mon, Aug 1, 2016 at 4:53 PM, James Keener <span dir="ltr"><<a href="mailto:jim@jimkeener.com" target="_blank">jim@jimkeener.com</a>></span> wrote:<br /><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div>Beyond just PostGIS, postgresql is a much better database on most fronts than mysql.<br />
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If you have two tables, one with geometries and one with densities, they both need to have the same id somewhere. Once you have the join key, you can perform a join , not a union, to get a result set containing both the geometry and the density. You can use raw SQL in qgis, but I tend to create a view in the database based on the query and the qgis will treat that as a table, more or less.<br />
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Jim<br /><br /><div class="gmail_quote"><div><div class="h5">On August 1, 2016 7:35:18 PM EDT, Chuck Young <<a href="mailto:wylie1066@gmail.com" target="_blank">wylie1066@gmail.com</a>> wrote:</div></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div class="h5">
<div dir="ltr"><div><div><div>I have been using databases for years and have used QGIS since 1.8 for general mapping. I know it can use additional data attached to the geographic data via a union query to display lots of different things. I have map areas where population density would be nice to display using different background fill colors bases on that density. I just need a bit of a boost getting the idea as to how to start and which way to go.<br /><br /></div>I have been using the program with SpatiaLite database. Do I need to go tto the PostGis db? Most of my other data is currently in MySQL. <br /><br /></div>Thanks for amy advice / guidance!!<br /><br /></div>Chuck<br /></div>
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