I´m setting up an database for an archaeological project with PSQL. There I have a field "material" connected with a table "materials" containing things like metal, stone, etc. In a third table I have stored more specific data on the materials like "gold", "iron" or "tuff". They all cary an attribute to which material they belong.
Now I set up a custom form in QGIS which works quite well. But now to my problem: I want to choose a material in the first combobox and the specification in a second one. The entries of that field should be filtered by the first one. So when I choose "metal" in the first field the second field should just show me iron, gold and copper.