How to calculate the difference between two SQL queries

Question

I want to do subtraction between entotalitem and exotalitem, the query I am using is to retrieve data from the same table tbl_orders_data.

I tried creating 2 queries, the first one to retrieve entotalitem and the second one to retrieve exotalitem

$encheck  = DB::table('tbl_orders_data')
                ->select('slot_id', DB::raw('sum(total_item) as entotalitem'))
                ->where('id_order_data', 'like', 'PBM' . '%')
                ->groupBy('slot_id')
                ->pluck('entotalitem');

$excheck  = DB::table('tbl_orders_data')
                ->select('slot_id', DB::raw('sum(total_item) as extotalitem'))
                ->where('id_order_data', 'like', 'PBK' . '%')
                ->groupBy('slot_id')
                ->pluck('extotalitem');
$en = $encheck;
$ex = $excheck;
    
dd($en - $ex);

Do I only need to use one query? Or should I do 2 queries like I tried? Please help me, thank you

Answer 1

You can use conditional aggregation here:

$check = DB::table('tbl_orders_data')
    ->select('slot_id', DB::raw("sum(case when id_order_data like 'PBM%' then total_item else 0 end) -
                                 sum(case when id_order_data like 'PBK%' then total_item else 0 end) as totalitem"))
    ->groupBy('slot_id')
    ->pluck('totalitem');