PowerShell to retrieve UserID of "Created By" user in a SharePoint List

[SamTech]

Good Day, how can I retrieve the unique "User ID" of the "Created By" or "Modified By" User?

#Get SQL column Definition for SharePoint List Field
Function Get-ColumnDefinition([Microsoft.SharePoint.SPField]$Field)
{
    $ColumnDefinition=""
    Switch($Field.Type)
    {
      "Boolean" { $ColumnDefinition = '['+ $Field.InternalName +'] [bit] NULL '}
      "Choice" { $ColumnDefinition = '['+ $Field.InternalName +'] [nvarchar](MAX) NULL '}
      "Currency" { $ColumnDefinition = '['+ $Field.InternalName +'] [decimal](18, 2) NULL '}
      "DateTime" { $ColumnDefinition = '['+ $Field.InternalName +'] [datetime] NULL '}
      "Guid" { $ColumnDefinition = '['+ $Field.InternalName +'] [uniqueidentifier] NULL '}
      "Integer" { $ColumnDefinition = '['+ $Field.InternalName +'] [int] NULL '}
      "Lookup" { $ColumnDefinition = '['+ $Field.InternalName +'] [nvarchar] (500) NULL '}
      "MultiChoice" { $ColumnDefinition = '['+ $Field.InternalName +'] [nText] (MAX) NULL '}
      "Note" { $ColumnDefinition = '['+ $Field.InternalName +'] [nText] NULL '}
      "Number" { $ColumnDefinition = '['+ $Field.InternalName +'] [decimal](18, 2) NULL '}
      "Text" { $ColumnDefinition = '['+ $Field.InternalName +'] [nVarchar] (MAX) NULL '}
      "URL" { $ColumnDefinition = '['+ $Field.InternalName +'] [nvarchar] (500) NULL '}
      "User" { $ColumnDefinition = '['+ $Field.InternalName +'] [nvarchar] (255) NULL '}     
      default { $ColumnDefinition = '['+ $Field.InternalName +'] [nvarchar] (MAX) NULL '}
  }
  return $ColumnDefinition
}

#Function to get the value of given field of the List item
Function Get-ColumnValue([Microsoft.SharePoint.SPListItem] $ListItem, [Microsoft.SharePoint.SPField]$Field)
{
    $FieldValue= $ListItem[$Field.InternalName]
     
    #Check for NULL
    if([string]::IsNullOrEmpty($FieldValue)) { return 'NULL'}
     
    $FormattedValue = ""
     
    Switch($Field.Type)
    {
    "Boolean"  {$FormattedValue =  Format-BooleanValue($FieldValue)}
    "Choice"  {$FormattedValue = Format-StringValue($FieldValue)}
    "Currency"  {$FormattedValue = $FieldValue}
    "DateTime"  {$FormattedValue = Format-DateValue($FieldValue)}
    "Guid" { $FormattedValue = Format-StringValue($FieldValue)}
    "Integer"  {$FormattedValue = $FieldValue}
    "Lookup"  {$FormattedValue = Format-LookupValue($FieldValue) }
    "MultiChoice" {$FormattedValue = Format-StringValue($FieldValue)}
    "Note"  {$FormattedValue = Format-StringValue($Field.GetFieldValueAsText($ListItem[$Field.InternalName]))}
    "Number"    {$FormattedValue = $FieldValue}
    "Text"  {$FormattedValue = Format-StringValue($Field.GetFieldValueAsText($ListItem[$Field.InternalName]))}
    "URL"  {$FormattedValue =  Format-StringValue($FieldValue)}
    "User"  {$FormattedValue = Format-UserValue($FieldValue) }
     #Check MMS Field
     "Invalid" { if($Field.TypeDisplayName -eq "Managed Metadata") { $FormattedValue = Format-MMSValue($FieldValue) } else { $FormattedValue =Format-StringValue($FieldValue)}  }
    default  {$FormattedValue = Format-StringValue($FieldValue)}
  }
  Return $FormattedValue
}

https://www.sharepointdiary.com/2016/06/export-sharepoint-list-data-to-sql-server-table-using-powers...

[#2]

@SamTech : Try below code:

$CreatedBy=$item["Author"]

$CreatedByObj = New-Object Microsoft.SharePoint.SPFieldUserValue($web, $CreatedBy)

$CreatedByUserID = $CreatedByUserObj.User.ID;

Hope it helps !

[#3]

@Ashish_Kohale I have added this suggested code but did not get any output for Author. Please advice where to add or modify the existing code

[#4]

@SamTech : Try replacing "Author" with Created By"