具有多态联接的Laravel查询生成器在SQLite上不起作用

Question

我有一个很大的Laravel查询生成器查询，这是它的最低版本

$query = DB::table('trainings')
            ->select(
                'trainings.id as training_id as training_id',
                'taggables.id as taggables_id',
                'taggables.tag_id as taggables_tag',
                'tags.id as tags_id',
                DB::raw('GROUP_CONCAT(tags.category) as tags_category'),
                DB::raw('GROUP_CONCAT(tags.value) as tags_value')
            )
            ->join('taggables', function($join) {
                $join->on('taggables.taggable_id', 'trainings.id')
                    ->where('taggables.taggable_type', 'App\\Training')
                ;
            })
            ->leftjoin('tags','tags.id','=','taggables.tag_id')
            ->groupBy('trainings.id')
            -get()
            ;

生成此sql：

select trainings.id as training_id,
taggables.id as taggables_id, 
taggables.tag_id as taggables_tag, 
tags.id as tags_id, 
GROUP_CONCAT(tags.category) as tags_category, 
GROUP_CONCAT(tags.value) as tags_value 

from trainings 

inner join taggables on taggables.id = trainings.id and taggables.taggable_type = "App\\Training"
left join tags on tags.id = taggables.tag_id 

group by trainings.id

结果是：

[当我在phpunit测试上运行相同的代码时（具有不同的数据+ sqlite），结果看起来像这样：

array:1 [
  0 => {#2579
    +"training_id": "2"
    +"taggables_id": "1"
    +"taggables_tag": "{"value":1,"category":1,"id":1}"
    +"tags_id": null
    +"tags_category": null
    +"tags_value": null
  }
]

出于某种原因，“ taggables_tag”返回相关标签表数据的JSON /对象，并且tag_-字段为空（可能是因为最后一个连接不起作用）。

任何想法如何解决此问题？

UPDATE

问题是联接，而不是group_concat：

$query = DB::table('trainings')
            ->join('taggables', function($join) {
                $join->on('taggables.taggable_id', 'trainings.id')
                    ->where('taggables.taggable_type', 'App\\Training')
                ;
            })
            ->get()

Returns:
    +"tag_id": "{"value":1,"category":1,"organisation_id":1,"updated_at":"2020-01-20 10:29:56","created_at":"2020-01-20 10:29:56","id":1}"
    +"taggable_id": "2"
    +"taggable_type": "App\Training"

Answer 1

我能够通过以下方式解决此问题：