php - 在 Laravel 中使用 IFNULL

Question

我在 laravel 中有一个查询，它工作正常。

$subjects = $app->db->table('subjects')->LeftJoin('downloads', 'subjects.subjectID', '=', 'downloads.subject_id')
        ->where('universityID', $currentUser->universityID)->where('semesterID', $currentUser->semesterID)->where('courseID', $currentUser->courseID)
        ->select('subjects.subjectID', 'subjects.subjectName', 'subjects.price',  'downloads.is_download' )
        ->orderBy('subjectID')
        ->get();

只有一个问题是，当表中没有相关条目时，is_download 会变为 null。经过一些研究，我发现有一个函数 IFNULL，我可以使用它来将 is_download null 更改为 0。所以这是我的查询，它不起作用。显示空白屏幕。

$subjects = $app->db->table('subjects')->LeftJoin('downloads', 'subjects.subjectID', '=', 'downloads.subject_id')
        ->where('universityID', $currentUser->universityID)->where('semesterID', $currentUser->semesterID)->where('courseID', $currentUser->courseID)
        ->select('subjects.subjectID', 'subjects.subjectName', 'subjects.price',  IFNULL( `downloads`.`is_download` , 0 ) )
        ->orderBy('subjectID')
        ->get();

我可以在我的 phpmyadmin 中编写此查询，但不知道如何在 laravel 中编写

这是 api，所以整个代码看起来像

use Illuminate\Database\Query\Expression as raw;
use project\Models\Subject;
use project\Models\Semester;
use project\Models\StudentRegistration;

$app->get('/api/getSubject/:studentID', function($studentID) use ($app) {
error_reporting(E_ALL);
    $currentUser = StudentRegistration::where('studentID', $studentID)->first();

$subjects = $app->db->table('subjects')->LeftJoin('downloads', 'subjects.subjectID', '=', 'downloads.subject_id')
        ->where('universityID', $currentUser->universityID)->where('semesterID', $currentUser->semesterID)->where('courseID', $currentUser->courseID)
        ->select('subjects.subjectID', 'subjects.subjectName', 'subjects.price',  IFNULL( `downloads`.`is_download` , 0 ) )
        ->orderBy('subjectID')
        ->get();
print_r($subjects);
    return $app->response->write(json_encode([
                'error' => 0,
                'subjects' => $subjects
    ]));
});

Answer 1

像这样尝试:

DB::Raw('IFNULL( `downloads`.`is_download` , 0 )');


$subjects = $app->db->table('subjects')->LeftJoin('downloads', 'subjects.subjectID', '=', 'downloads.subject_id')
    ->where('universityID', $currentUser->universityID)->where('semesterID', $currentUser->semesterID)->where('courseID', $currentUser->courseID)
    ->select('subjects.subjectID', 'subjects.subjectName', 'subjects.price',  DB::Raw('IFNULL( `downloads`.`is_download` , 0 )') )
    ->orderBy('subjectID')
    ->get();