问题:如何从连接中的一组记录中获取列的总和?

我有一个将文件退还给我的请求。我想把每个文件的货物总和汇总起来。

它看起来像这样:

有文件。

  +-------------+----------+
  | document_id | owner_id | 
  +-------------+----------+
  | 52f20e4d    | ef27737d |  
  | 3bfdc5aa    | ef27737d |   
  +-------------+----------+

每个文件都附有产品。

  +-------------+-------------+-----------+
  | product_id  | document_id | total_sum |
  +-------------+-------------+-----------+
  | b60624a7    | 52f20e4d    | 10        |
  | fcc21801    | 52f20e4d    | 5         |
  | d5cbe99d    | 3bfdc5aa    | 3         |
  | 5e537533    | 3bfdc5aa    | 4         |
  +-------------+-------------+-----------+

我的PHP代码:

$result = DB::table('documents as docs')->leftJoin('products as t_products', function($join) {
    $join->on('t_products.document_id', '=', 'docs.document_id');
})->where('docs.owner_id', '=', $currentUserId)->select('docs.document_id', 't_products.total_sum')
    ->get();

return response()->json($result);

我得到以下信息:

[
  {
      "document_id": "52f20e4d",
      "total_sum": "5"
  },

  {
      "document_id": "52f20e4d",
      "total_sum": "10"
  },

  {
      "document_id": "3bfdc5aa",
      "total_sum": "4"
  },

  {
      "document_id": "3bfdc5aa",
      "total_sum": "3"
  }
]

但我只想看到两个条目,其中总_sum 将被汇总。

像这样:

[
    {
        "document_id": "52f20e4d",
        "total_sum": "15"
    },

    {
        "document_id": "3bfdc5aa",
        "total_sum": "7"
    }
]

解答

按文档 ID 和总和添加分组

$result = DB::table('documents as docs')
    ->leftJoin('products as t_products', function($join) {
        $join->on('t_products.document_id', '=', 'docs.document_id');
    })
    ->where('docs.owner_id', '=', $currentUserId)
    ->selectRaw('docs.document_id, sum(t_products.total_sum) as total_sum')
    ->groupBy('docs.document_id')
    ->get();