Laravel SQl：如果不存在任何记录，如何返回0值

Question

I am trying to return a value of zero if no record in the transactions table exists. Right now if no transactions exists for a specific budget then I get nothing back. This is my query right now.Any help is appreciated. Below is an example of when I would need it to return 0 for fuel since no transaction exists for it. I clarified.

budgets table

_____________
id | name
1  | Groceries
2  | Fuel

transactions table

__________________
id | Category_id | Amount
1  | 1           | 30

Laravel code

 $budgets = Budget::join('transactions', 'budgets.id', '=', 'transactions.category','left outer')
   ->select([
      DB::raw('SUM(transactions.amount) / budgets.amount * 100 as percent'),
                        'budgets.category'
    ])
    ->where('transactions.user_id','=', $authId)
    ->where('budgets.user_id','=',$authId)
    ->whereBetween('transactions.created_at', array($first_day_this_month, $last_day_this_month))
    ->groupBy('budgets.category','budgets.amount')
    ->get();

Answer 1

Try this:

$budgets = array();
$budgets = Budget::join('transactions', 'budgets.id', '=', 'transactions.category','left outer')
                ->select([
                    DB::raw('SUM(transactions.amount) / budgets.amount * 100 as percent'),
                    'budgets.category'
                ])
                ->where('transactions.user_id','=', $authId)
                ->where('budgets.user_id','=',$authId)
                ->whereBetween('transactions.created_at', array($first_day_this_month, $last_day_this_month))

                ->groupBy('budgets.category','budgets.amount')
                ->get();

if( count($budgets) == 0 )
{
    return 0;
}
else
{
    return $budgets;
}

Explanation: Initially the $budgets is an blank array() , after running the query if still the array is blank means query do not return any data. In that case return 0, otherwise the data array.

Answer 2

You should use COALESCE function:

substitute

DB::raw('SUM(transactions.amount) / budgets.amount * 100 as percent'), 
'budgets.category'

with

DB::raw('COALESCE(SUM(transactions.amount), 0) / budgets.amount * 100 as percent'), 
'budgets.category'