Feature request #4136: Symbolizing field from a table joined to a joined table - QGIS Application - QGIS Issue Tracking

Feature request #4136

Symbolizing field from a table joined to a joined table

Added by Bernhard Ströbl over 12 years ago. Updated about 10 years ago.

Status:	Closed
Priority:	Normal
Assignee:	-
Category:	Symbology
Pull Request or Patch supplied:	No	Resolution:	wontfix
Easy fix?:	No	Copied to github as #:	14116

Description

situation: Three layers:
t1 PostGIS table with two fields: id (integer, PK), the_geom
t2 PostgreSQL table with many fields containing two datasets for each dataset of t1; fields: id(integer), type (integer) in this case it is not relevant, that there are two datasets in t2 for each in t1 as the value in type is the same for both
t3 PostgreSQL table with two fields: id (integer), typename (varchar) containing lookup-values for field type in t2

Steps to do:
a) Join t2 to t1 on t1.id = t2.id
b) Join t3 to t1 on t1.type = t3.id
c) style t1 categorized on field type => works
d) style t1 categorized on field typename => does not work (categorization works but layer is not displayed on map)

tried with 1.8.0-Trunk (QGIS-Codeversion 58c737d) installed via osgeo-installer

expl.zip - example data (2.07 KB) Bernhard Ströbl, 2011-08-09 11:17 PM

History

#1 Updated by Marco Hugentobler over 12 years ago

Can you dump the three tables (or similar ones that can reproduce the bug) to shapes and attach them to the ticket?

Thanks,
Marco

#2 Updated by Bernhard Ströbl over 12 years ago

File expl.zip added

Hi Marco,

attached zip file contains a shape file and two csv. files.
Do as follows:
1) load them into QGIS
2) in expl_lines - layer properties join expl_data (join field = nr, target field = nr)
3) in expl_lines - layer properties join expl_lookup (join field = id, target field = typnr (note this field comes from expl_data!))
4) in expl_lines change style from "single symbol" to "categorized" (column = typ), click classify and apply => classification works but the line is not visible any more

#3 Updated by Marco Hugentobler over 12 years ago

Tracker changed from Bug report to Feature request

Ah, I see. Yes, QGIS does not provide the capability to join multiple tables like that. Every join needs to have a target field in the origin layer. Otherwise, it would be quite complicated to manage the join dependencies (QGIS fetches only the necessary attributes for rendering).
I've changed the join dialog to only show original attributes as target and thus this ticket to feature request.

#4 Updated by Bernhard Ströbl over 12 years ago

Ok, I see. Thank you for your effort. This is definitely not a "must have". I could still classify on typenr but wanted to avoid writing the legend labels :-)