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I have installed QGIS 2.12 Lyon and I need to dissolve multiple polygons according to one column in the dbf file (my layer is a shapefile).

I have used SAGA "Polygon dissolve by attribute" algorithm and it works OK. The issue is that in my original file I have 7 columns, one of which is used to dissolve the polygons. The dbf file of the new layer has only 1 field - the one used to dissolve polygons.

How do I force SAGA to keep my other fields?

I just need one entry for each new polygon - information is repeated anyway.

Using the interface I could not see any option to select a method to retain information for other fields.

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  • What if the other columns have different contents? Should the values be written as comma separated list or what? – user30184 Nov 6 '15 at 17:35
  • Hi. For this specific set of data I did not mind, since I knew that all those fields had repeated values for the same dissolving records. Ideally there should be a list of different options depending on the field type. For example, for a string there should be: first, last, max, min, distinct list, full list, count. For numeric, I would expect min, max, sum, mean, median, count. – Michele Nov 10 '15 at 21:52
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Not exactly what I wanted but it's a workaround. I have imported both layers in QGIS. On my new layer I selected "Properties", then selected "Joins". I have added a new Join and set up as: Join layer: old layer Join field: field used to dissolve polygons Target field: the only field in the table Choose which field are joined: checked the box and selected few fields from the original file.

Clicked OK and my new layer dbf file has additional fields.

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