Php 如何使用Elount或query builder连接两个表

我有一个查询，它基本上列出了两个用户共有的主题

$subcommon= SubjectUser::selectRaw('topic_id, count(topic_id) AS aggregate')
     ->whereIn('user_id', [4, 2])->groupBy('topic_id')
     ->having('aggregate','>',1)->get();

例如，下表的查询结果为

{"topic_id":3,"aggregate":1} 

表一

id|user_id|topic_id
 1|2      |3
 2|4      |3
 3|5      |1

我还有另一个表（tabletwo），它也有我想要加入的topic_id，这样我就可以从第二个表中获得第2行的查询结果。我该怎么做呢

表二

id|group_id|topic_id
 1|6      |2
 2|7      |3
 3|7      |1

试试这个

$subcommon= DB::table('tableone')
     ->selectRaw('topic_id, count(topic_id) AS aggregate')
     ->join('tabletwo','tabletwo.topic_id', '=', 'tableone.topic_id')
     ->whereIn('user_id', [4, 2])
     ->groupBy('tableone.topic_id')
     ->having('aggregate','>',1)
     ->get();

---

我仍然可以将

subjectuiser

模型加入到表名中，因为我似乎无法使其正常工作

$subcommon= DB::table('tableone')
     ->selectRaw('topic_id, count(topic_id) AS aggregate')
     ->join('tabletwo','tabletwo.topic_id', '=', 'tableone.topic_id')
     ->whereIn('user_id', [4, 2])
     ->groupBy('tableone.topic_id')
     ->having('aggregate','>',1)
     ->get();