QGIS – Join Attributes

By David Crowther

Question:

How do you Join Attributes from one Table to another in QGIS? 

Answer:

QGIS has a tool called Join Attributes that allows you to append the attributes from one table to the attributes in another table. For example, you may have Point locations that you wish to update with a geographic location, based on the boundary each point falls within.

In our example we will Join Attributes from the County Table (polygons) where the Hospitals (points) are geographically within a County boundary.

Use the Search window and search for the Join Attributes tool.

In the Join Attributes window, choose the Input layer to be the points (Hospitals) and the Join Layer to be the polygons (County). Specify that the geometric relationship is where the Hospitals are within the Counties.

In the Fields to Add option tick and choose the fields from the County layer that you wish to Join to the Hospitals. In this case we have chosen the File_Name field as this contains the County Name.

Choose to create a Temporary Layer or save as a new GIS file. Once the Process has been RUN view the new layer in the map and notice that it will be an exact copy of the original Hospital (points) layer.

However if you open the Attribute window you can see that the County Name (FILE_NAME field) has been appended to each Hospital point

Note – any Point records that are not within a boundary will still be listed but will have a blank value in the Join(s) field.

If you select a record and zoom to its location you can see that the Joined County Name is correct.