Combine 2 result set using union in Kusto

Question

I want to combine 2 result set into one. Requirement: I am working on "Workbook" in azure and trying to add a drop-down as a parameter.I need to add values in the drop down using query. I retrieved the running apps from below query. I need to add custom value to the result set.

Table 1: (Holds all the Function Apps running)

let AvailableApps = customEvents
| summarize by operation_Name 
| order by operation_Name asc;

I need to combine one value to the above result set ie: "All Apps" .

How can we achieve it. I tried altering below code to suit mine,

let Range10 = view () { range MyColumn from 1 to 10 step 1 };

Can anyone shed some light on this.

Sorry if this is a duplicate question.

Edited: I figured out one way, Let me know if this is the best approach.

let AvailableApps = customEvents
| summarize by operation_Name 
| order by operation_Name asc;
let DefaultValue = datatable (operation_Name:string)
    ["All Apps"];
union DefaultValue,AvailableApps;

Answer 1

When dealing with Drop Down parameters you can add an "All" choice from within the workbook UI that will be appended to the result set of the kusto query. For example:

See the docs for more info.