Laravel: left join query

问题

I have such SQL query, which works fine:

SELECT A.program_id FROM A
LEFT JOIN B
ON A.program_id = B.program_id
WHERE
B.program_id IS NULL

But i want it to rewrite into LARAVEL style, like this:

\DB::table('A')
->join('B', 'A.program_id', '=', 'B.program_id')
->select('A.program_id')
->whereNull('B.program_id')
->get()->toArray();

But this code returns me 0 results.

回答1:

You are using join instead of left join

Try this

\DB::table('A')
->leftjoin('B', 'A.program_id', '=', 'B.program_id')
->select('A.program_id')
->whereNull('B.program_id')
->where('A.student_id', '=', 5)
->get()->toArray();

It will produce a query like

来源：https://stackoverflow.com/questions/44928276/laravel-left-join-query