Gotcha. Yeah, there's a "Rerun Analysis" option for the resulting layers, but it's going to create a new layer, as opposed to feeding into the existing one.
To do it all with the web tools would involve a new layer → export the new layer to file → use file to overwrite existing layer. More clicking than you'd probably want, but maybe not too bad if it's only quarterly.
Do you have any desktop tools (Esri or otherwise) you could use to create the joined layer? If the layer is published from a file or a service definition, you can very easily overwrite it.
- Josh Carlson
Kendall County GIS