Sql error in laravel 5.4

Here I joined 2 tables addprojects and users. But It show me error. How can I fix it?

$test= addproject::select('addprojects.id','addprojects.proj_name',DB::raw("DATEDIFF(addprojects.proj_starts,addprojects.proj_end)AS Days"))
                                ->join('user', 'users.emp_id', '=', 'addprojects.emp_id')
                                ->where('id', 1)->get();

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