Taking 2 overlapping spatial polygon layers and creating 1 with features from one replacing those of other layer?

Question

I have two sf multipolygon layers - one is a 5km buffer along the Mexico-US border and the other is an administrative 2-level layer of Mexico. I am trying to figure out how to layer these on top of one another and have the final product be one layer that can be visualized like this:

I have tried spatially joining with st_join, however this results in either just the border polygon with attributes from the admin 2 layer (listing buffer layer first) or in the admin 2 layer with buffer layer attributes. I am looking to get one layer with the polygons from both and attributes in overlapping areas to be defined by the buffer layer.

Answer 1

You can do this in two steps:

1. Erase the area of the buffer from the administrative 2-level layer using the ST_Difference function.
2. Add the buffer polygon to the resulted layer using the ST_Union function.