用ADO的Recordset打开表时是把所有的记录都读出来，当表的内容很多时（我要处理的表中有400多万条记录，表中又无可以帮助分段的列如自动增长的列），打开占用内存非常大，经常出现内存不足。我在处理过程中必须一条一条的处理。请问有无办法每次读出1000条（即第一次1－1000，第二次1001―2000），或者通过编程在此表中增加一列，给每条记录编号（或类似于ACCESS数据库的自动增长），请问如果可以通过这两种方法实现，能否给出代码。现谢谢拉！
调试欢乐多
另外,不要设置记录集为Client属性,只有在对每条记录取数据时,才从服务器返回数据,而不是在打开记录集时,就返回所有记录集数据到客户端,这样增加了客户程序的内存占用.
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" \
no_namespace rename("EOF", "EndOfFile")
#include <stdio.h>
#include <ole2.h>
#include "conio.h"
#include "AbsolutepageX.h"//Function Declarations.
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void AbsolutePageX(void);
void PrintProviderError(_ConnectionPtr pConnection); ///////////////////////////////////////////////////////////
// //
// Main Function //
// //
///////////////////////////////////////////////////////////
void main()
{
if(FAILED(::CoInitialize(NULL)))
return;
AbsolutePageX(); ::CoUninitialize();
}
/////////////////////////////////////////////////////////////
// //
// AbsolutePageX Function //
// //
/////////////////////////////////////////////////////////////void AbsolutePageX(void)
{ // Define ADO object pointers.
// Initialize pointers on define.
// These are in the ADODB:: namespace.
_RecordsetPtr pRstEmployees = NULL;
//Define Other Variables
//Interface Pointer declared.(VC++ Extensions)
IADORecordBinding *picRs = NULL;
CEmployeeRs emprs; //C++ class object
HRESULT hr = S_OK;
_bstr_t strMessage; //Open a recordset using a Client Cursor
//For the Employee Table _bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';"
"Initial Catalog='pubs';Integrated Security='SSPI';"); try
{
// Open a recordset.
TESTHR(hr = pRstEmployees.CreateInstance(__uuidof(Recordset))); // Use client cursor to enable Absoluteposition property.
pRstEmployees->CursorLocation = adUseClient; // You have to explicitly pass the default Cursor type
// and LockType to the Recordset here
TESTHR(hr = pRstEmployees->Open("employee",
strCnn,adOpenForwardOnly,adLockReadOnly,adCmdTable)); //Open an IADORecordBinding interface pointer which we'll use for
//Binding Recordset to a class
TESTHR(hr = pRstEmployees->QueryInterface
(__uuidof(IADORecordBinding), (LPVOID*)&picRs)); //Bind the Recordset to a C++ Class here
TESTHR(hr = picRs->BindToRecordset(&emprs)); //Display Names and hire dates, five records at a time
pRstEmployees->PageSize = 5; int intPageCount = pRstEmployees->PageCount;
for(int intPage=1;intPage<=intPageCount;intPage++)
{
pRstEmployees->put_AbsolutePage((enum PositionEnum)intPage);
strMessage = ""; for(int intRecord=1;
intRecord<=pRstEmployees->PageSize;intRecord++)
{
printf("\t%s %s %.10s\n",
emprs.lau_fnameStatus == adFldOK ?
emprs.m_szau_fname : "<NULL>",
emprs.lau_lnameStatus == adFldOK ?
emprs.m_szau_lname : "<NULL>",
emprs.lau_hiredateStatus == adFldOK ?
emprs.m_szau_hiredate : "<NULL>"); pRstEmployees->MoveNext(); if(pRstEmployees->EndOfFile)
break;
} printf("\n Press any key to continue...");getch(); //Clear the Screen for the next Display
system("cls");
}
}
catch(_com_error &e)
{
// Notify the user of errors if any.
_variant_t vtConnect = pRstEmployees->GetActiveConnection(); // GetActiveConnection returns connect string if connection
// is not open, else returns Connection object.
switch(vtConnect.vt)
{
case VT_BSTR:
printf("Error:\n");
printf("Code = %08lx\n", e.Error());
printf("Message = %s\n", e.ErrorMessage());
printf("Source = %s\n", (LPCSTR) e.Source());
printf("Description = %s\n", (LPCSTR) e.Description());
break;
case VT_DISPATCH:
PrintProviderError(vtConnect);
break;
default:
printf("Errors occured.");
break;
}
}
// Clean up objects before exit.
//Release the IADORecordset Interface here
if (picRs)
picRs->Release(); if (pRstEmployees)
if (pRstEmployees->State == adStateOpen)
pRstEmployees->Close();
}///////////////////////////////////////////////////////////
// //
// PrintProviderError Function //
// //
///////////////////////////////////////////////////////////void PrintProviderError(_ConnectionPtr pConnection)
{
// Print Provider Errors from Connection object.
// pErr is a record object in the Connection's Error collection.
ErrorPtr pErr = NULL; if( (pConnection->Errors->Count) > 0)
{
long nCount = pConnection->Errors->Count;
// Collection ranges from 0 to nCount -1.
printf("Error:\n");
for(long iError = 0; iError < nCount; iError++)
{
pErr = pConnection->Errors->GetItem(iError);
printf("\t Error number: %x\t%s\n", pErr->Number,
(LPCSTR) pErr->Description);
}
}
}
//EndAbsolutePageCppAbsolutePageX.h:// BeginAbsolutePageH
#include "icrsint.h"
//This Class extracts only fname,lastname and hire_date class CEmployeeRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CEmployeeRs)
//Column fname is the 2nd field in the table
ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_szau_fname,
sizeof(m_szau_fname), lau_fnameStatus, FALSE) ADO_VARIABLE_LENGTH_ENTRY2(4, adVarChar, m_szau_lname,
sizeof(m_szau_lname), lau_lnameStatus, TRUE) ADO_VARIABLE_LENGTH_ENTRY2(8, adVarChar, m_szau_hiredate,
sizeof(m_szau_hiredate), lau_hiredateStatus, TRUE)
END_ADO_BINDING()public:
CHAR m_szau_lname[41];
ULONG lau_lnameStatus;
CHAR m_szau_fname[41];
ULONG lau_fnameStatus;
CHAR m_szau_hiredate[40];
ULONG lau_hiredateStatus;
};
// EndAbsolutePageH