Symbolize by Graduated Colors with Too Few Values

RogerDunnGIS

I am using ArcGIS Pro 3.4.0.  I have added an SQL query layer to my map.  The underlying SQL joins a feature class with a table in a different database.  Since it is an inner join, only features with associated data appear in the map and attribute table.  This query layer will basically give a number to 0 or more features which are found in the joined table.  To reiterate, I am not using ArcGIS Pro's "layer join" feature; rather, I have added a query layer to a map which uses the JOIN operator in pure SQL.

Although the GIS layer has many points, the joined table currently only has one valid record.  Obviously this will change over time.  We're expecting numbers between about -1,000 and 1,000.

The goal is to symbolize this query layer by Graduated Color.  Low numbers will be bright blue while high numbers will be light blue.

My challenge is that only one row is present in the query layer at this time.  Because of this, I seem to be unable to add more breaks, no matter the Method.  I have tried selecting "Natural Breaks (Jenks)", "Equal Interval", "Defined Interval" and "Manual Interval".  None of these choices offer me the ability to add breaks for future anticipated number values.

If I select "Natural Breaks (Jenks)" or "Equal Interval", and change the number of Classes to a number greater than 1, ArcGIS Pro sets the Classes back to 1, and assigns a default point symbol.

If I select "Defined Interval", any Interval Size I choose yields a warning at the top of the symbology pane, "Unable to classify layer.  Select a different classification method".

If I select "Manual Interval", Classes is disabled (by design).  I don't see how to add any symbols or breaks to the Classes table.

I have tried using the context menu, the Histogram tab, and the Scales tab to add more classes to any of these graduated color methods, to no avail.

Feel free to recommend that I try this or that.  However, I won't accept a solution that involves adding a bunch of dummy data into our production system just to satisfy the Graduated Colors symbology pane.  Thank you so much, community!

MErikReedAugusta

I've run into similar issues where I write a custom Arcade symbology script that merges two or more fields, but where all possible values don't currently exist in the underlying dataset, so I can't pre-create the symbology for them.  (See here for an idea post to help alleviate that problem).

The case study there isn't directly relevant to your problem, but the current workaround is.

1. Create a fake feature class that mimics your query layer in geometry and schema.
2. Fill the fake feature class with dummy data that spans your predicted range
3. Symbolize as appropriate
4. On your Query Layer, run "Import Symbology" and point it at the dummy feature class.
5. It should hopefully retain the symbolic ranges, if we're lucky.
6. You may now delete the fake feature class.

(N.B. In my case, I created fake data points on the live layer, and then just deleted and/or discarded the edits after the symbology was set, but in your case an entirely separate fake feature class is probably the better approach.)

I've never tested it with graduated symbols, but I know it works with class-based symbols.