如何用相同序列的正常值获得空值

Question

我要从数据库中获取数据，包括空值，显示在concat作为查询工作的数据库结构的数据和查询结果附加图像，我要所有的答案值，包括空值

以下是我的疑问；

$list = Modelname::where('cid', 293)
    ->whereIn('qid',[7, 8, 9, 10, 11, 12])
    ->select('created_at')
    ->selectRaw('GROUP_CONCAT(answer) as answer')
    ->groupBy('created_at')
    ->get();

查询结果：

{"created_at":"2021-03-15T01:12:12.000000Z","username":"managers","item":"6,6,6,6,6","ids":"1881,1882,1883,1884,1885","qids":"19,20,21,22,23"},

我的数据库结构

Answer 1

您可以使用mysql IfNull将空结果作为字符串获取：

$list = Modelname::where('cid', 293)
    ->whereIn('qid',[7, 8, 9, 10, 11, 12])
    ->select('created_at')
    ->selectRaw('GROUP_CONCAT(CONCAT(answer, '=', 
                 IFNULL(answer, 'NULL'))) as answer')
    ->groupBy('created_at')
    ->get();

Answer 2

只需尝试使用或where()方法。

示例：

$list = Modelname::where('cid', 293)
    ->whereIn('qid',[7, 8, 9, 10, 11, 12])
    ->orWhere('qid', null) // orWhere here
    ->select('created_at')
    ->selectRaw('GROUP_CONCAT(answer) as answer')
    ->groupBy('created_at')
    ->get();

或者只将null添加到数组中，如下所示：

$list = Modelname::where('cid', 293)
    ->whereIn('qid',[7, 8, 9, 10, 11, 12, null]) // null here
    ->select('created_at')
    ->selectRaw('GROUP_CONCAT(answer) as answer')
    ->groupBy('created_at')
    ->get()