php - How to add where inside DB::raw() in laravel

I'm want to get the completed orders amount, and the rejected orders count in 1 query. Please see my code below. How can I add where or condition inside the DB::raw()?

return DB::table('restaurants')
->join('orders', 'restaurants.id', 'orders.restaurant_id')
->select([
   DB::raw('SUM(orders.total) WHERE status = 8 as completed_sum'),
   DB::raw('COUNT(DISTINCT(orders.transaction_code)) WHERE status = 3 as rejected_count')
])
->get();

Error

SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax;

Update

When I try ->toSql(), I get this:

select `restaurant_name` as `restaurant`, SUM(total) WHERE status = 8 as completed_sum,
COUNT(DISTINCT(transaction_code)) WHERE status = 3 as rejected_count from `restuarants` inner join `orders` on
`restuarants`.`id` = `orders`.`restaurant_id` where `orders`.`date` between ? and ? group by `restuarants`.`id`

Solution:

id didn't got the chance to test it ... but it supposed to work

->select([
   DB::raw('SUM(CASE WHEN status = 8 THEN orders.total END) completed_sum'),
   DB::raw('COUNT(DISTINCT IF(status = 3,orders.transaction_code,null)) as rejected_count')
])

for sum with condition see:mysql sum

for count with distinct with if see this answer