VC中如何用ADO查询数据！

Question

不是用SQL语句，而是在打开的数据库中查询的，类似C++Builder中的Locate方法。

Answer 1

用Find 跟 C++Builder中的Locate方法 相同而且功能要强大

Answer 2

用 Recordset 打开数据库 ， 用Recordset 的Find 方法

Answer 3

// BeginFindCpp
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" \
    no_namespace rename("EOF", "EndOfFile")#include <ole2.h>
#include <stdio.h>
#include <conio.h>
#include "FindX.h"// Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void FindX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);//////////////////////////////////////////////////////////
//                                                      //
//      Main Function                                   //
//                                                      //
//////////////////////////////////////////////////////////void main()
{
    if(FAILED(::CoInitialize(NULL)))
        return;    FindX();    //Wait here for the user to see the output.
    printf("Press any key to continue...");
    getch();
    ::CoUninitialize();
}//////////////////////////////////////////////////////////
//                                                      //
//             FindX Function                           //
//                                                      //
//////////////////////////////////////////////////////////void FindX(void) 
{
    HRESULT    hr = S_OK;    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
    _ConnectionPtr    pConnection  = NULL;
    _RecordsetPtr     pRstTitles   = NULL;
    IADORecordBinding   *picRs     = NULL;  //Interface Pointer declared.
    CTitlesRs titlers;                      //C++ class object    _bstr_t strCnn("Provider=sqloledb;Data Source=MyServer;"
            "Initial Catalog=pubs;Integrated Security=SSPI;");    try
    {
        // Open connection.
        TESTHR(pConnection.CreateInstance(__uuidof(Connection)));
        pConnection->Open (strCnn, "", "", adConnectUnspecified);        // Open title Table
        TESTHR(pRstTitles.CreateInstance(__uuidof(Recordset)));
        
        pRstTitles->Open("SELECT title_id FROM titles",
            _variant_t((IDispatch *)pConnection), 
            adOpenStatic, adLockReadOnly, adCmdText);        // The default parameters are sufficient to search forward
        // through a Recordset.        pRstTitles->Find ("title_id LIKE 'BU%'",0,adSearchForward,"");        //Open an IADORecordBinding interface pointer which 
        //we'll use for Binding Recordset to a class    
        TESTHR(pRstTitles->QueryInterface(
            __uuidof(IADORecordBinding),(LPVOID*)&picRs));        //Bind the Recordset to a C++ Class here    
        TESTHR(picRs->BindToRecordset(&titlers));        // Skip the current record to avoid finding the same 
        // row repeatedly. The book is redundant because Find 
        // searches from the current position.
        int count = 0;        //Continue if last find succeeded.
        while (!(pRstTitles->EndOfFile)) 
        {
            printf("Title ID: %s\n",titlers.lt_titleidStatus == adFldOK ?
                titlers.m_szt_titleid : "<NULL>");
            count++;                       //Count the last title found.            _variant_t  = pRstTitles->Book;  //Note current pos.
            pRstTitles->Find("title_id LIKE 'BU%'", 1, adSearchForward, 
                );
        }        //Release IADORecordset Interface
        if (picRs)
            picRs->Release();        // Clean up objects before exit.
        pRstTitles->Close();
        pConnection->Close();
        printf("The number of business titles is %d\n",count);   }

Answer 4

catch(_com_error &e)
   {
       // Notify the user of errors if any.
       // Pass a connection pointer accessed from the Recordset.
       PrintProviderError(pConnection);
       PrintComError(e);
   }
}//////////////////////////////////////////////////////////
//                                                      //
//       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.
        for(long i = 0; i < nCount; i++)
        {
            pErr = pConnection->Errors->GetItem(i);
            printf("\t Error number: %x\t%s", pErr->Number, 
                (LPCSTR)pErr->Description);
        }
    }
}//////////////////////////////////////////////////////////
//                                                      //
//       PrintComError Function                         //
//                                                      //
//////////////////////////////////////////////////////////void PrintComError(_com_error &e)
{
   _bstr_t bstrSource(e.Source());
   _bstr_t bstrDescription(e.Description());    // Print Com errors.
   printf("Error\n");
   printf("\tCode = %08lx\n", e.Error());
   printf("\tCode meaning = %s\n", e.ErrorMessage());
   printf("\tSource = %s\n", (LPCSTR) bstrSource);
   printf("\tDescription = %s\n", (LPCSTR) bstrDescription);
}
// EndFindCppFindX.h// BeginFindH
#include "icrsint.h"//This Class extracts only titleId from Titles table.
class CTitlesRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CTitlesRs)    // Column title_id is the 1st field in the recordset 
    // from Titles table.
    ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_szt_titleid, 
         sizeof(m_szt_titleid), lt_titleidStatus, FALSE)END_ADO_BINDING()public:
   CHAR   m_szt_titleid[150];
   ULONG   lt_titleidStatus;
};
// EndFindH