jak utworzyć zapytanie MySql, aby wyświetlić saldo bieżące z kredytów i debetów, gdy wielu klientów ma indywidualne salda

To powinno działać

  select  transaction_id, customer_id, date, credit, debit,
  abs(sum(ifnull(credit,0)) over (partition by customer_id order by date,credit,transaction_id ) - sum(ifnull(debit,0)) over(partition by customer_id order by date,debit,transaction_id)) as balance
  from ledger
  order by transaction_id;