Question

我有数千行的视觉狐狸专业数据库。我正在使用oledb从fox pro获取数据并将其导出（在进行一些计算和填充之后）到sql server。我已经使用数据集一次填充2-3个数据表（相关表）。

第一个问题是内存使用非常高，因为数据集很大。我想减少内存占用。对此提出了任何建议。

所以我决定一次获取几行。如何使用oledb命令获取行，以便我可以获取例如1-20然后20-40等

Answer 1

string queryString = "SELECT OrderID, CustomerID FROM Orders WHERE ORDERID >= @StartOrderID AND ORDERID <= @EndOrderID";

    using (OleDbConnection connection = new OleDbConnection(connectionString))
    {
        OleDbCommand command = new OleDbCommand(queryString, connection);
        command.Parameters.Add(new OleDbParameter("@StartOrderID", "PASS THE VALUE HERE"));
        command.Parameters.Add(new OleDbParameter("@EndOrderID", "PASS THE VALUE HERE"));

        connection.Open();
        OleDbDataReader reader = command.ExecuteReader();

        while (reader.Read())
        {
//Retrieve records here
        }
        reader.Close();
    }

Answer 2

根据所有评论和HatSoft的代码，我认为您正在寻找。这是伪代码，这意味着它不会编译，但应该让你很好地了解从这里去的地方。

int NumberOfRecordsToRetrieve = 10000;
int StartRecordNumber = 1;
bool EndOfFile = false;

 string queryString = "SELECT OrderID, CustomerID FROM Orders WHERE RECNO() BETWEEN @StartRecordNumber AND @EndRecordNumber"; 

While (!EndOfFile)
{
     using (OleDbConnection connection = new OleDbConnection(connectionString)) 
     { 
         OleDbCommand command = new OleDbCommand(queryString, connection); 
         command.Parameters.Add(new OleDbParameter("@StartRecordNumber", StartRecordNumber)); 
         command.Parameters.Add(new OleDbParameter("@EndRecordNumber", StartRecordNumber + NumberOfRecordsToRetrieve)); 

         connection.Open(); 
         OleDbDataReader reader = command.ExecuteReader(); 

          EndOfFile = true;
          while (reader.Read()) 
          { 
               EndOfFile = false

               //Retrieve records here and do whatever process you wish to do
           } 
           reader.Close(); 

           StartRecordNumber += NumberOfRecordsToRetrieve;
     } 
}

oledb，视觉狐狸亲和c＃

2 个答案: