In QGIS, I have one layer (called 'All data shapefile') which is a shapefile with my entire set of data, and another layer (called 'Y_data') that is also a shape file with a subset of 'All data shapefile'. The subset was determined by making a buffer around certain key data points and extracting all data points within 100m radius of the key points to make this second layer.
In the 'All data shapefile' layer I have a column named 'ID' which gives a unique number ID for each datapoint, however I added this column after creating 'Y_data', so the latter layer does not have the ID column.
How do I append the 'ID' column into the 'Y_data' layer, ensuring that each data point will have the same ID in both layers (i.e. each data point is given its correct ID as determined by 'All data shapefile')?
When I try to use 'Join', the pictures indicate what I end up with in my 'Y_data' attribute table: