php - 在关系上选择查询未在 laravel eloquent 中给出结果

Question

records = Student::with(array('Mark' => function($marks)
    {
    $marks->select(DB::raw('sum(obtain_marks)'))->with(array('Subject' => function($subject){
    $subject->orderby('subject_name')->select(DB::raw('count(subjects.id)','sum(total_marks)','subject_name'));
        }));
    }))->where('id', $id)->get();

为什么这没有执行？

它在 mysql 中工作 select count(subjects.id),sum(subjects.total_marks),sum(marks.obtain_marks),subjects.subject_name from students 内部连接标记 students.id = 标记.student_id 内部连接subjects.id = mark.subject_id where students.id = 20 group by subject.subject_name; 它在mysql中工作。

Answer 1

在 Select 您必须选择您拥有本地密钥的列

$records = Student::with(['Mark' => function($marks){
    $marks->select(DB::raw('sum(obtain_marks)'), 'Subject_id' /* same Problem here ->select('subject_id')*/)->with(['Subject' => function($subject){
        $subject->orderby('subject_name')
                ->select(DB::raw('count(subjects.id)','sum(total_marks)','subject_name'));
    }]);
}])
->where('id', $id)
->select('Mark_id') // you must select foreign key column to use relationship
->get();