Deneb Sorting Issue when "Datum" is included

Hi vamshi_pbims, and thanks for the details.

I'm not good enough at DAX to solve the first problem, but solving the second may help. You'll need to validate this, though.

The strategy here of using datum to substitute the value of 'Target' is an interesting approach, and will sort of work, but doesn't fulfill the requirement of having a sort order that can be unioned also. Additionally, because of how Vega-Lite unions scales with a sort clause, you will need an aggregate of min, max, count or a boolean value in there. This is provided as a warning in Vega Editor:

For some reason, this doesn't appear in Deneb; I'll have to have a look at why that is.

As such, the approach I've taken is to:

1. Aggregate the target value using a transform
2. Calculate a field called MonthYear for this layer after aggregation, with a value of 'Target'
3. Calculate a field called SortOrd for this layer after aggregation with a value of 999912 (which would be akin to a 'no date' row in a date dimension).

This layer's dataset will look as follows in the debugger:

These fields and values now match the "shape" of the primary layer and will resolve. The only other thing to do is to add an aggregate to the sort clause. Because the scale is grouped by the granularity of the data, either a max or a min will be OK.

Here's the resulting output:

I've made a couple of additional changes to the encoding channels, as they work hierarchicallyin Vega-Lite. Revised spec is as follows:

{
  "data": {
    "name": "dataset"
  },
  "transform": [
    {
      "filter": "datum['Sum Of Price'] != null "
    }
  ],
  "layer": [
    {
      "mark": {
        "type": "bar",
        "tooltip": true
      },
      "encoding": {
        "y": {
          "field": "Sum Of Price"
        }
      }
    },
    {
      "transform": [
        {
          "aggregate": [
            {
              "field": "Target_m",
              "op": "sum",
              "as": "Target_m"
            }
          ]
        },
        {
          "calculate": "'Target'",
          "as": "MonthYear"
        },
        {
          "calculate": "999912",
          "as": "SortOrd"
        }
      ],
      "mark": {
        "type": "bar",
        "tooltip": true
      },
      "encoding": {
        "y": {
          "field": "Target_m"
        }
      }
    }
  ],
  "encoding": {
    "x": {
      "field": "MonthYear",
      "sort": {
        "field": "SortOrd",
        "op": "min"
      },
      "type": "ordinal"
    },
    "y": {
      "type": "quantitative"
    }
  }
}

I've also attached an updated copy of your workbook, so hopefully you can have a look, test and see if this solves problem #1 as well.

Thanks!

Daniel