php - 我想连接两个表，在基本模型中，它们的 id 在 Laravel 中是未知的，我不知道如何获取准确的结果

Question

我正在尝试从faculties表中获取数据。但我选择了注册。基本上我的想法是显示使用教师姓名和部分注册的类(class)

我尝试了所有连接，但没有任何效果。我很困惑如何在 Laravel Eloquent 中进行 subjoin。

$results = Enrollment::select(
               'students.rollnumber as student_rollnumber',
               'courses.name as course_name',
               'courses.course_code',
               'sections.name as section_name',
               'faculties.fname as faculty_fname',
               'faculties.lname as faculty_lname'
           )->join(
               'courses',
               'courses.id',
               'enrollments.course_id'
           )->join(
               'students',
               'students.id',
               'enrollments.student_id'
           )->join(
               'sections',
               'sections.id',
               'enrollments.section_id'
           )->join(
               'faculties',
               'faculties.section_id',
               'enrollments.section_id'
           )->join(
               'faculty_course_details',
               'faculties.id',
               'faculty_course_details.faculty_id'
           )->where('enrollments.student_id',9)
            ->get();

错误:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'faculties.fname' in 'field list' (SQL: select students.rollnumber as student_rollnumber, courses.name as course_name, courses.course_code, sections.name as section_name, faculties.fname as faculty_fname, faculties.lname as faculty_lname from enrollments inner join courses on courses.id = enrollments.course_id inner join students on students.id = enrollments.student_id inner join sections on sections.id = enrollments.section_id where enrollments.student_id = 9)

Answer 1

您在加入院系和院系_类(class)_详细信息时犯了错误。您正在使用列section_id加入学院，而学院表中没有section_id列

首先加入(faculty_course_details.section_id、enrollments.section_id)上的faculty_course_details，然后加入(faculties.id、faculty_course_details.faculty_id)上的学院，如下所示

$results = App\Enrollment::select(
           'students.rollnumber as student_rollnumber',
           'courses.name as course_name',
           'courses.course_code',
           'sections.name as section_name',
           'faculties.fname as faculty_fname',
           'faculties.lname as faculty_lname'
        )->join(
           'courses',
           'courses.id',
           'enrollments.course_id'
        )->join(
           'students',
           'students.id',
           'enrollments.student_id'
        )->join(
           'sections',
           'sections.id',
           'enrollments.section_id'
        )->join(
           'faculty_course_details',
           'faculty_course_details.section_id',
           'enrollments.section_id'
        )->join(
           'faculties',
           'faculties.id',
           'faculty_course_details.faculty_id'
        )
        ->where('enrollments.student_id',9)
        ->get();

您将得到如下输出:

[
    {
       "student_rollnumber": "dummy_878wegy6",
       "course_name": "dummy_course",
       "course_code": "dummy_123",
       "section_name": "dummy_name",
       "faculty_fname": "John", 
       "faculty_lname": "Doe"
    }
]