Laravel Query Builder - sum() method issue

If one needs to select SUM of a column along with a normal selection of other columns, you can sum select that column using DB::raw method:

DB::table('table_name')
    ->select('column_str_1', 'column_str_2', DB::raw('SUM(column_int_1) AS sum_of_1'))
    ->get();

You don't need to use select() or get() when using the aggregate method as sum:

$purchases = DB::table('transactions')
    ->join('categories', 'transactions.category_id', '=', 'categories.id')
    ->where('categories.kind', '=', 1)
    ->sum('transactions.amount');

Read more: http://laravel.com/docs/5.0/queries#aggregates