第二个查询

Question

有两个表 customer_invoice 和 sold_item_details

customer_invoice表中的
• 有列， cus_inv_id （PK）
• 此 cus_inv_id 是sold_item_details的外键

这是我对代码的抽象视图，

public void txtRent_PreviewKeyDown(object sender, KeyEventArgs e){

    /* This method will Insert values to the customer_invoice table */
    CreateOrder();

   /* This method will Insert values to the sold_item_details table*/
   InsertOrderItem(OrderItem orderItem);
}

这是我的问题，当执行插入查询时，第二个查询引发了一个无法添加或更新子行的MysqlException。我在 CreateOrder（）和InserOrderItem（）之间签入了插入过程是否已经令人惊讶地完成，结果证明它已成功。

例如，如果我使用 cus_inv_id = 1 插入值设置，则会将其插入 customer_invoice 表中，但在插入 sold_item_details 表时 cus_inv_id（FK）= 1 会引发该异常。

这两个与这两种方法相关的代码。 （为了解决问题，我删除了一些列）

public void CreateOrder()
    {
       _connection.open();
        var mysqlTrans = _connection.BeginTransaction();
        var orderId = -1;
        MySqlDataReader sqlDataReader;

        try
        {
            const string query =
                "SELECT cus_inv_id FROM customer_invoice " +
                "WHERE customer_id = @cusId";

            var mysqlCommand1 = new MySqlCommand(query, _connection, mysqlTrans);
            mysqlCommand1.Parameters.AddWithValue("@cusId", customerId);
            sqlDataReader = mysqlCommand1.ExecuteReader();

            if (sqlDataReader.HasRows)
            {
                sqlDataReader.Read();
                orderId = (int) sqlDataReader["cus_inv_id"];
            }
            sqlDataReader.Close();

            if (orderId == -1)
            {
                var mysqlCommand2 = _connection.CreateCommand();
                mysqlCommand2.Connection = _connection;
                mysqlCommand2.Transaction = mysqlTrans;

                mysqlCommand2.CommandText = "SELECT MAX(cus_inv_id) FROM customer_invoice " +
                                            "HAVING MAX(cus_inv_id) IS NOT NULL";

                sqlDataReader = mysqlCommand2.ExecuteReader();
                if (sqlDataReader.Read())
                {
                    orderId = (int) sqlDataReader["MAX(cus_inv_id)"] + 1;
                }
                else
                {
                    orderId += 2; 
                }

                sqlDataReader.Close();

                mysqlCommand2.CommandText =
                    "INSERT INTO customer_invoice(cus_inv_id)" +
                    " VALUES(@cusInvId)";

                mysqlCommand2.Parameters.AddWithValue("@cusInvId", orderId);
                mysqlCommand2.ExecuteNonQuery();
            }
            mysqlTrans.Commit();
            _connection.close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex);
            mysqlTrans.Rollback();
        }
    }

 public void InsertOrderItem(OrderItem orderItem)
    {
        _connection.open();
        var mysqlCommand = _connection.CreateCommand();
        var mysqlTrans = _connection.BeginTransaction();
        mysqlCommand.Connection = _connection;
        mysqlCommand.Transaction = mysqlTrans;
        try
        {
            mysqlCommand.CommandText = "SELECT MAX(sold_item_id) FROM sold_item_details " +
                                       "HAVING MAX(sold_item_id) IS NOT NULL";

            var sqlDataReader = mysqlCommand.ExecuteReader();
            var lastSoldItemId = 1;
            if (sqlDataReader.Read())
            {
                lastSoldItemId = (int) sqlDataReader["MAX(sold_item_id)"] +1;
            }

            sqlDataReader.Close();

            mysqlCommand.CommandText = "INSERT INTO sold_item_details(sold_item_id,cus_inv_id) VALUES(@soldItemId, @cusInvId)";

            mysqlCommand.Parameters.AddWithValue("@soldItemId", lastSoldItemId);

            mysqlCommand.Parameters.AddWithValue("@cusInvId", orderItem.OrderId);

            mysqlCommand.ExecuteNonQuery();
            mysqlTrans.Commit();
            _connection.close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
            mysqlTrans.Rollback();
        }
    }