如何与Laravel进行左外连接？

Question

我想要一个表中的信息,以及是否还有来自另一个表的匹配信息.

这是我的代码

 $scoreObject = DB::table('responses')
        ->select('responses.id', 'responses.questions_id', 'responses.answer_id', 'responses.open_answer', 'responses.user_id',  'responses.scan_id',
             'questions.question', 'questions.question_nr', 'questions.type', 'questions.totalsection_id',
            'answers.id as answerID', 'answers.answer', 'answers.questions_id', 'answers.points'
        )
        ->Join('answers as answers', 'responses.answer_id', '=', 'answers.id')
        ->Join('questions as questions', 'answers.questions_id', '=', 'questions.id')
        ->orderBy('questions.id', 'ASC')
        ->where('responses.scan_id', $scanid)
        ->where('responses.user_id', $userid)
        ->groupBy('questions.id')
        ->get();

它返回所有与答案匹配的答案(answers.questions_id questions.id').一些响应没有匹配(因为没有respond.answer_id)但我仍然想要响应信息.

我怎样才能在laravel中获得这样一个左外连接？

Answer 1

您可以尝试将连接指定为左外连接:

->join('answers as answers', 'responses.answer_id', '=', 'answers.id', 'left outer')

join方法的第四个参数是$type,未指定时,默认为该值inner.但是由于左连接和左外连接是相同的,所以你可以改用leftJoin它来使它更具可读性:

->leftJoin('answers as answers', 'responses.answer_id', '=', 'answers.id')