Unable to execute multiple Oracle queries in C#

Question

In the following code when I try to update amount in the table t_payment, I expect it to be set the value of Convert.ToInt32(request.amount+ previous_paid_amount); whereas previous_paid_amount is assumed to be 0 instead of getting updated. So I am unable to use the updated value of previous_paid_amount variable.

Any help would be highly appreciated. Thanks

double previous_paid_amount = 0;
try {
  OracleCommand command2 = new OracleCommand();

  command2.CommandText = "select amount from t_payment where penalty_order_id = (select id from t_penalty_order where protokol_no = :invoiceNumber)";

  command2.Parameters.Add(new OracleParameter(@"invoiceNumber", OracleDbType.Varchar2, 255)).Value = request.invoiceNumber;

  command2.Connection = connection;
  command2.CommandType = System.Data.CommandType.Text;

  using (OracleDataReader row2 = command.ExecuteReader()) {
    while (row2.Read()) {
      previous_paid_amount = Convert.ToInt32(row2.GetValue(0));
    }
  }
}
catch (Exception e) {
  completePayment.code = 111;
  completePayment.message = e.Message;
  completePayment.transactionNumber = null;
}

// update the paid amount by adding the current amount
try {
  OracleCommand command2 = new OracleCommand();

  command2.CommandText = "Update t_payment set amount = :amount where penalty_order_id = (select id from t_penalty_order where protokol_no = :invoiceNumber)";

  command2.Parameters.Add(new OracleParameter(@"amount", OracleDbType.Int32)).Value = Convert.ToInt32(request.amount+ previous_paid_amount);
  command2.Parameters.Add(new OracleParameter(@"invoiceNumber", OracleDbType.Varchar2, 255)).Value = request.invoiceNumber;

  command2.Connection = connection;
  command2.CommandType = System.Data.CommandType.Text;
  command2.ExecuteNonQuery();
}
catch (Exception e) {
  completePayment.code = 111;
  completePayment.message = e.Message;
  completePayment.transactionNumber = null;
}

Answer 1

I suggest executing just one query (we don't want to do extra work by querying Oracle twice , fetching data to the workstation then pushing at again to Oracle). As far as I can see from your

"Update t_payment set amount = :amount where penalty_order_id = (select id from t_penalty_order where protokol_no = :invoiceNumber)";

code, you want to update t_payment table by adding some extra money to amount field with condition applied:

update t_payment
   set amount = amount + SOME_EXTRA_MONEY
 where penalty_order_id in (select p.id 
                              from t_penalty_order p
                             where p.protokol_no = :invoiceNumber) 

We have to determine what is SOME_EXTRA_MONEY : we can try to derive it from query

"select amount from t_payment where penalty_order_id = (select id from t_penalty_order where protokol_no = :invoiceNumber)";

So we have (I've added Sum in case we have several records, and that's why should sum them and Nvl in case we have none - in this case extra sum is 0 ):

update t_payment
   set amount = amount + (select Nvl(Sum(t.amount), 0) 
                            from t_payment t 
                           where t.penalty_order_id in (select p.id 
                                                          from t_penalty_order p
                                                         where p.protokol_no = :invoiceNumber))
 where penalty_order_id in (select p.id 
                              from t_penalty_order p
                             where p.protokol_no = :invoiceNumber)

Time to execute this query:

 using (OracleCommand command2 = new OracleCommand()) {
   command2.CommandText =
     @"update t_payment
          set amount = amount + (select Nvl(Sum(t.amount), 0) 
                                   from t_payment t 
                                  where t.penalty_order_id in (select p.id 
                                                                 from t_penalty_order p
                                                                where p.protokol_no = :invoiceNumber))
        where penalty_order_id in (select p.id 
                                     from t_penalty_order p
                                    where p.protokol_no = :invoiceNumber)";

   command2.Parameters.Add(
     new OracleParameter(@"invoiceNumber", OracleDbType.Varchar2, 255)
   ).Value = request.invoiceNumber;

   command2.ExecuteNonQuery();
 } 

Answer 2

It didn't work because you are using command instead of command2.

using (OracleDataReader row2 = command.ExecuteReader())

This needs to be modified with

 using (OracleDataReader row2 = command2.ExecuteReader())