VC中如何用ADO查询数据！

[午秋]

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。

[Pipi0714]

为什么呢？

[freelove1]

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

[午秋]

Find怎么用呀！

[freelove1]

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

[ZHENG017]

// 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 bookmark 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 mark = pRstTitles->Bookmark; //Note current pos.
pRstTitles->Find("title_id LIKE 'BU%'", 1, adSearchForward,
mark);
}

//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);

}

[ZHENG017]

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);
}
// EndFindCpp

FindX.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