The Data Operation – Select action can return an array of objects or an array of arrays. It should also be able to return an array of primitives. This is very basic map functionality that is used to extract properties from an array of objects, often as a prerequisite for a Join.
Example use cases:
Extract email addresses from an array of people, which are then joined to create an email list.
Extract ID numbers from an array of objects, which are then joined to create a SQL WHERE IN clause.
Current workarounds include putting a Compose or an Append-To-Array-Variable inside an Apply-To-Each. The Compose method cannot be used inside a nested loop and the Append-To-Array-Variable method cannot be used with concurrent loops.