Question

            // conn is read from handydrive
            //conn2 read from C:\

此代码用于将新记录写入C：\中的DB，首先检查是否存在。我的问题对于很多记录来说太慢了。以及如何提高它... ...

        SqlCeCommand cmd1 = new SqlCeCommand("Select * from bill_discount  ", conn);

        SqlCeDataReader dr1 = cmd1.ExecuteReader();

        while (dr1.Read() != false)
        {
            SqlCeCommand cmd4 = new SqlCeCommand("Select * from bill_discount where bill_no='" + dr1.GetInt32(0) + "' AND bill_shopdc='" + dr1.GetString(2) + "'  ", conn2);

            SqlCeDataReader dr4 = cmd4.ExecuteReader();
            if (dr4.Read() == false)
            {
                SqlCeCommand cmd2 = new SqlCeCommand("INSERT INTO bill_discount (bill_no,bill_value,bill_shopdc) VALUES ('" + dr1.GetInt32(0) + "','" + dr1.GetDouble(1) + "','" + dr1.GetString(2) + "') ", conn2);

               // SqlCeDataReader dr2 = cmd2.ExecuteReader();
                cmd2.ExecuteNonQuery();

            }

        }
        //-------------------------------------------------------------------

Answer 1

我会看一下SqlBulkCopy Class：

让您有效地批量加载SQL 服务器表包含来自另一个的数据源。

BTW ：在上面的代码中，选择整个bill_discount表并不是一个好主意，特别是如果表格很大。

[此外，您似乎可以执行单个TSQL语句，而不是循环遍历每一行并向数据库进行往返。]

此示例应该有所帮助：SqlBulkCopy - Copy Table Data Between SQL Servers at High Speeds - ADO.NET 2.0 New Feature

Answer 2

让我们从使代码更具可读性开始。结果如下：

SqlCeCommand getAllBills = new SqlCeCommand("select * from bill_discount", primaryConnection);
SqlCeDataReader allBillsReader = getAllBills.ExecuteReader();
while (allBillsReader.Read())
{
    SqlCeCommand getBill = new SqlCeCommand("select * from bill_discount where bill_no = '" + allBillsReader.GetInt32(0) + "' and bill_shopdc = '" + allBillsReader.GetString(2) + "'  ", secondaryConnection);
    SqlCeDataReader billReader = getBill.ExecuteReader();
    if (!billReader.Read())
    {
        SqlCeCommand addMissingBill = new SqlCeCommand("insert into bill_discount (bill_no, bill_value, bill_shopdc) values ('" + allBillsReader.GetInt32(0) + "', '" + allBillsReader.GetDouble(1) + "', '" + allBillsReader.GetString(2) + "')", secondaryConnection);
        addMissingBill.ExecuteNonQuery();
    }
}

必须处置一次性物品。我们来做吧。

我们也删除SQL注入。

最后，让我们优化第二个查询：如果您只想检查数据库中是否存在该值，则无需选择某些内容并执行阅读器。

using (SqlCeCommand getAllBills = new SqlCeCommand("select bill_no, bill_value, bill_shopdc from [bill_discount]", primaryConnection))
{
    using (SqlCeDataReader allBillsReader = getAllBills.ExecuteReader())
    {
        while (allBillsReader.Read())
        {
            using (SqlCeCommand getBill = new SqlCeCommand("if exists(select * from [bill_discount] where [bill_no] = @billNumber and bill_shopdc = @billShop) select 1 else select 0", secondaryConnection))
            {
                getBill.Parameters.AddWithValue("@billNumber", allBillsReader["bill_no"]);
                getBill.Parameters.AddWithValue("@billShop", allBillsReader["bill_shopdc"]);

                bool billExists = Convert.ToBoolean(getBill.ExecuteScalar());
                if (!billExists)
                {
                    using (SqlCeCommand addMissingBill = new SqlCeCommand("insert into [bill_discount] ([bill_no], [bill_value], [bill_shopdc]) values (@billNumber, @billValue, @billShop)", secondaryConnection))
                    {
                        addMissingBill.Parameters.AddWithValue("@billNumber", allBillsReader["bill_no"]);
                        addMissingBill.Parameters.AddWithValue("@billValue", allBillsReader["bill_value"]);
                        addMissingBill.Parameters.AddWithValue("@billShop", allBillsReader["bill_shopdc"]);

                        int countAffectedRows = addMissingBill.ExecuteNonQuery();
                        Debug.Assert(countAffectedRows == 1, "The data was not inserted.");
                    }
                }
            }
        }
    }
}

所以我们在这里。

现在，它仍然是一种低性能解决方案。为了更有效，您可能希望在带有连接的单个SQL查询中执行相同的操作。由于两个表可能位于不同的服务器上，因此您可以查看链接服务器：一种功能，可以对来自多个服务器的多个表执行单个查询。

Answer 3

我看到你正在使用SqlCe，它在插入批量数据时有许多限制。主要限制是实际的SqlCe引擎。但是，您可以通过使用直接表插入来绕过它：

using (var command = connection.CreateCommand())
                     {
                         command.Transaction = transaction;
                         command.CommandType = CommandType.TableDirect;
                         command.CommandText = TABLE_NAME_IN_SQL;

                         using (var rs = command.ExecuteResultSet(ResultSetOptions.Updatable))
                         {
                             var rec = rs.CreateRecord();
                             rec.SetInt32(0, value0); // the index represents the column numbering
                             rec.SetString(1, value1);
                             rec.SetInt32(2, value2);
                             rs.Insert(rec);
                         }
}

如何改进这段代码

3 个答案: