Get all objects from database that are not in a relationship yet - php

Question

I have the following query and it's doing it's job fine:
SELECT exams.id, exams.date FROM exams
WHERE exams.modul_id = (SELECT questions.modul_id FROM questions where questions.id = 5)
AND NOT EXISTS (
SELECT * FROM exam_question, questions
WHERE questions.id = 5
AND questions.id = exam_question.question_id
AND exam_question.exam_id = exams.id
)
It returns me all exams that belong to the same model as exam but not connteced to exam yet.
I want to use this query in Laravel but I always get an empty result back (it shouldn't be empty)
DB::table('exams')
->select(['id', 'date'])
->whereRaw('modul_id = '.$question->modul_id)
->whereNotExists(function ($query) use ($question) {
$query->select(DB::raw(1))
->from('questions as q')
->join('exam_question as eq', 'q.id', '=', 'eq.question_id')
->join('exams as e', 'eq.exam_id', '=', 'e.id')
->whereRaw('q.id = '.$question->id);
})
->get();
The output of the laravel expression is:
select `id`, `date` from `exams` where modul_id = 1 and not exists (select 1 from `questions` as `q` inner join `exam_question` as `eq` on `q`.`id` = `eq`.`question_id` inner join `exams` as `e` on `eq`.`exam_id` = `e`.`id` where q.id = 5)

Answer 1

I see problem in your sql query dump in section and not exists (... you select starts with select 1 from it will always select number 1 from your table according to selected rows count
select `id`, `date` from `exams`
where modul_id = 1
and not exists (
select 1 from `questions` as `q`
inner join `exam_question` as `eq` on `q`.`id` = `eq`.`question_id`
inner join `exams` as `e` on `eq`.`exam_id` = `e`.`id` where q.id = 5)
You have to use in query builder instead $query->select(DB::raw(1)) ... -> $query->select('*') ...
DB::table('exams')
->select(['id', 'date'])
->whereRaw('modul_id = '.$question->modul_id)
->whereNotExists(function ($query) use ($question) {
$query->select('*')
->from('questions as q')
->join('exam_question as eq', 'q.id', '=', 'eq.question_id')
->join('exams as e', 'eq.exam_id', '=', 'e.id')
->whereRaw('q.id = '.$question->id);
})
->get();
If the rest logic which you used to create your query is correct it will start to work