Showing the result of a datasubset inside a paging grid

Question

I have the datasubset A shows all managers of my firm . i am showing inside a paging grid . 
 
 Data subset A has a key value Manager ID 
 
 for each manager i am querying employees ( Data Subset B ) who reports to that manager . which i am getting by passing the manager ID from the Datasubset A 
 I have to display managers and their direct reports in a single paging grid . as shown below

Manager ID 
 Manager Name 
 Designation 
 Direct Reports

12 
 John 
 Sr Manager 
 Don;Kaila;Arun

I did the following steps 
 1) Wrote an expression rule to query all the managers and stored in Datasubset A 
 2) For each manager ID in Datasubset A , i wrote another expression rule to query direct reports 
 
 So i have two data subsets which i have to display in one grid . do you know how to accomplish this ?

Mike Schmitt · Accepted Answer

Sorry - I made a small mistake. The inner a!forEach() needs to be wrapped inside a concat(). My original example is now updated.

Mike Schmitt · Answer

for your Direct Reports column, something like this template should work well: 
 a!gridTextColumn(
 data: a!forEach(
 local!managerDataSubset,
 with(
 local!reportsForThisManager: rule!queryReportsForMgr(mgrId: fv!item.mgrId),
 concat(
 a!forEach(
 local!reportsForThisManager,
 fv!item.FirstName & " " & fv!item.LastName & if(fv!isLast, null(), char(10))
 )
 )
 )
 )
)