如何从sql中的每一行值计算

I have a table named general_ledger from which I need to show dr_amount, cr_amount and the balance between them as running_balance. That's why I have written a query that is given below. But I am getting the result of each query like the balance only of current row. But I need to produce the result with the remaining balance. Suppose First row dr_balance is 20000 and cr_balance is 5000 and remaining balance is 15000. In second row only cr_balance is 5000. Now the result should be 10000 with the deduction but my result is -5000. I have no idea how to fix this. Can anyone please help me on this? I need your help very much. Here is my query given below :I have a table named general_ledger from which