【CSV】カラムごとにファイルを分割する方法

氏名,年齢,性別,部署
太郎,103,男,総務部
次郎,132,男,総務部
三郎,22,男,経理部
花子,13,女,総務部
花子２号,13,女,経理部
花子３号,142,女,いきものがかり
花子４号,17,女,経理部

"氏名","年齢","性別","部署"
"太郎","103","男","総務部"
"次郎","132","男","総務部"
"花子","13","女","総務部"

"氏名","年齢","性別","部署"
"花子２号","13","女","経理部"
"三郎","22","男","経理部"
"花子４号","17","女","経理部"

"氏名","年齢","性別","部署"
"花子３号","142","女","いきものがかり"

# csv読み込み場所を指定
$csv = "c:\sample.csv"

# 出力先フォルダ
$outFolder = "c:\tempfolder\"

# csvインポート（部署ごとに並び替えて抽出していることが重要）
$ImportCsv = Import-Csv $csv -Encoding Default | Sort-Object @{Expression="部署";asc=$true}

##### start #####
# 配列作成
$exCsv = @();

# 1行目を示すダミーを入力
$tempDep  = "dummy"

# インポートしたCSVを1行ずつ読み込む
foreach($line1 in $ImportCsv){
    # 最初のレコードでない かつ 前レコードと部署が異なる
    if(($tempDep -ne "dummy") -and ($tempDep -ne $line1."部署")){
        # 部署名の名前でファイル出力
        $exCsv | Export-Csv -NoTypeInformation -Path ($outFolder + $tempDep + ".csv") -Encoding Default
        
        # 配列をリセット
        $exCsv = @();
    }
    $exCsv += $line1         # 配列にレコード追加
    $tempDep = $line1."部署" # 前レコードの部署として次回ループ用に格納
}
# ループ処理最後の所属のエクスポート
$exCsv | Export-Csv -NoTypeInformation -Path ($outFolder + $tempDep + ".csv") -Encoding Default

"氏名","年齢","性別","部署"
"花子３号","142","女","いきものがかり"
"花子２号","13","女","経理部"
"三郎","22","男","経理部"
"花子４号","17","女","経理部"
"太郎","103","男","総務部"
"次郎","132","男","総務部"
"花子","13","女","総務部"