I have a problem in QGIS. I have an attribute table (no geographical information), which contains owners of parcels and an ID for every row.
Then I have a shapefile, which contains polygons and an attribute table which contains an ID (Fits with the owner information).
If I want to join these two parts, QGIS joins only one owner per parcel, even if there are 5.
How can I manage it, that finally there is a row in the attribute table of the shapefile, containing all owners and not only one?
There are a few concepts you have to know.
A join is a 1-to-1-relation: one parcel with one owner. If you do a join in QGIS then it will take the first corresponding owner and join it to the parcel
A relation is normally defined as 1 to many. This is your case. Here you have to define the relation through project > projectproperties > relations. Here you can set the relation-definitions. When you open the features dialogue, you will see every connected owner in an embedded table.
If you want to only have 1 row and all the owners in 1 field, you can use SQL or QGIS-expressions.
SQL
suppose you have following layers:
parcels:
owners:
Go to DB-manager > virtual layers > qgis layers. Open an sql-window and execute:
select parcel.*, group_concat(owner) as owners from parcel
left join owners on parcel.id = owners.parcel_id
group by owners.parcel_id
Load the results as a new layer
