powershell - 世代管理

> 対象DIR
> sampleDB_2021-11-20_17-00-00.bak
> sampleDB_2021-11-21_17-00-00.bak
> sampleDB_2021-11-22_17-00-00.bak
> sampleDB_2021-11-23_17-00-00.bak

# 2件残して後は削除
Get-ChildItem |
  Sort-Object -Property Name -Descending |
  Select-Object -Skip 2 |
  ForEach-Object {
    Remove-Item $_.FullName
}