It is a fairly common task to get only distinct values from an array. That means only those values, that are not duplicates.
Imagine you have the following array:
If you want only distinct values from this array, that means you want [ "A", "B", "C", "D"] without the duplicate "A".
As you can guess from the previous screenshot, this can be done with the union() function, that is available in both Logic Apps and Power Automate. The actual purpose of this function is to create a union between two arrays or objects:
Returns a single array or object with all the elements that are in either array or object passed to this function.
👉 union() - Reference guide for expression functions - Azure Logic Apps
A side effect of this function is, that each element is returned only once. That means creating a union of an array either with itself or with an empty array will result in an array that contains only distinct values.
The expression in our example would be:
union(variables('myArray'), json('[]'))
The expression json('[]') is an easy way to create an empty array for the union.