QGIS: concatenate_unique several columns in attributes table

How do I merge columns in an attribute table in QGIS?

Open the layer properties (double-click the layer) and click on the Joins tab in the left column. Click the green Addition symbol at the bottom of the dialog box. Change the Join layer to the standalone table and change the join and target fields to the fields that have a common geographic identifier. Click OK.
 

How do I combine attributes in QGIS?

Quote from video: So here you click right on your layer double click and in properties you will find join.

How do I group fields in QGIS?

Quote from video: Just click select all layers. And add selected layers to project now my all layers are visible here so i want to group them in point line and area so i will make group like i want point in one group.