Add Lookup Field to SharePoint List using PowerShell

PowerShell script to add lookup field to SharePoint list:

Scenario: You have a parent list called "Parent Projects" and child list "Project Milestones". The "Parent Project Name" field in child list is being looked up from the parent list's "Project Name" field.

PowerShell to Add Lookup Field to SharePoint List:

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue 

#configuration parameters
$WebURL="https://portal.crescent/Projects/"
$ParentListName="Parent Projects"
$ChildListName="Project Milestones"

$ParentLookupColumnName="Project Name"
$ChildLookupColumnName="Parent Project Name"

#Get the Parent and Child Lists
$Web = Get-SPWeb $WebURL
$ParentList = $web.Lists[$ParentListName]
$ChildList = $web.Lists[$ChildListName]

#Check if Field exists already
if(!$childList.Fields.ContainsField($ChildLookupColumnName))
{
    #sharepoint powershell - create lookup field
    $ChildLookupColumn = $ChildList.Fields.AddLookup($ChildLookupColumnName,$ParentList.id,$False)
    $ChildLookupColumn = $ChildList.Fields[$ChildLookupColumnName]

    #Setup lookup Field property
    $ChildLookupColumn.LookupField = $ParentList.Fields[$ParentLookupColumnName]
    #$ChildLookupColumn.AllowMultipleValues=$true
    $ChildLookupColumn.update()
    write-host "Lookup field added successfully!" -f green
}
else
{
    write-host "Field Exists already!" -f red
}

That's all! We've created lookup column using PowerShell in SharePoint list.