I have a shapefile whose features I can filter by specifying a where clause in the query dialogue. F.x. I have a field named 'city_name' and by stating 'city_name = "London"' in the where clause only London is displayed. What I would like to do now is to fetch all values in 'city_name' from the attribute table.
Something like that:
select distinct city_name from [attribute table]
I found several tools in QGIS apparently dealing with SQL and I also had a quick look at the different Plugins. But I fail at connecting to a database or the table name ... what database or which table in that case?
In the end I want to export the result list and use it for further processing.
I am using QGIS 1.8.