[Sitecore] Find items of a type, read a multilist field from there, get those items and summarise the relationship.

gistfile1.ps1

$courses = gci -r | where-object { $_.TemplateName -ne $null -and $_.TemplateName -eq 'CoursePage' }

ForEach ($course in $courses) {
 
   $subjectAreaField = $course.SubjectArea
   
   if ($subjectAreaField)
   {
       $subjectAreaIDs = $subjectAreaField -split '\|'
       $subjectArray = @()
       
       foreach ($areaID in $subjectAreaIDs)
       {
          $subjectArea = get-item master: -ID $areaID
          
          if ($subjectArea) {
            $subjectArray += $subjectArea.Name.Trim()
          }
       }
       
       $result = '"' + $course.Name.Trim() + '","' + ($subjectArray -join ",") + '"'
       
       Write-Host $result
   }
}