Laravel 对某一列进行筛选然后求和sum()的例子

这个例子是对课程进度表里面的某个学生的剩余课时进行求和汇总。 laravel 版本是 lts 5.5 StudentLessonProgress::where('student_info_id', $student_info_id) ->sum('total_left_class_num'); 打印sql语句如下: array:1 [▼ 0 => array:3 [▼ “query” => “select sum(total_left_class_num) as aggregate from student_lesson_progress where student_info_id