C/C++ code
_RecordsetPtr m_pRec;
m_pRec->Open("SELECT * FROM 地址",
_variant_t((IDispatch*)m_pCon,true),
adOpenStatic,
adLockOptimistic,
adCmdText);能不能具体分析下Open函数。
_RecordsetPtr m_pRec;
m_pRec->Open("SELECT * FROM 地址",
_variant_t((IDispatch*)m_pCon,true),
adOpenStatic,
adLockOptimistic,
adCmdText);能不能具体分析下Open函数。
本范例在已打开的 Recordset 和 Connection 对象上使用 Open 和 Close 方法。// BeginOpenCpp
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" \
no_namespace rename("EOF", "EndOfFile")#include <oledb.h>
#include <stdio.h>
#include <conio.h>
#include "OpenX.h"// Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void OpenX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);///////////////////////////////////////////////////////////
// //
// Main Function //
// //
///////////////////////////////////////////////////////////void main()
{
if(FAILED(::CoInitialize(NULL)))
return; OpenX(); ::CoUninitialize();
}///////////////////////////////////////////////////////////
// //
// OpenX Function //
// //
///////////////////////////////////////////////////////////void OpenX(void)
{
// Define ADO object pointers.
// Initialize pointers on define.
// These are in the ADODB:: namespace
_RecordsetPtr pRstEmployee = NULL;
_ConnectionPtr pConnection = NULL; // Define string variables.
_bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';"
"Initial Catalog='pubs';Integrated Security='SSPI';"); // Define Other Variables.
HRESULT hr = S_OK;
IADORecordBinding *picRs = NULL; // Interface Pointer declared.
CEmployeeRs emprs; // C++ Class object
DBDATE varDate; try
{
// open connection and record set
TESTHR(pConnection.CreateInstance(__uuidof(Connection)));
pConnection->Open(strCnn,"","",adConnectUnspecified); TESTHR(pRstEmployee.CreateInstance(__uuidof(Recordset)));
pRstEmployee->Open("Employee",
_variant_t((IDispatch *)pConnection,true), adOpenKeyset,
adLockOptimistic, adCmdTable); // Open an IADORecordBinding interface pointer which we'll
// use for Binding Recordset to a class.
TESTHR(pRstEmployee->QueryInterface(
__uuidof(IADORecordBinding),(LPVOID*)&picRs)); //Bind the Recordset to a C++ Class here.
TESTHR(picRs->BindToRecordset(&emprs)); // Assign the first employee record's hire date
// to a variable, then change the hire date.
varDate = emprs.m_sze_hiredate;
printf("\nOriginal data\n");
printf("\tName - Hire Date\n");
printf(" %s %s - %d/%d/%d\n\n",
emprs.le_fnameStatus == adFldOK ?
emprs.m_sze_fname : "<NULL>",
emprs.le_lnameStatus == adFldOK ?
emprs.m_sze_lname : "<NULL>",
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.month : 0,
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.day : 0,
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.year : 0); emprs.m_sze_hiredate.year=1900;
emprs.m_sze_hiredate.month=1;
emprs.m_sze_hiredate.day=1;
picRs->Update(&emprs); printf("\nChanged data\n");
printf("\tName - Hire Date\n");
printf(" %s %s - %d/%d/%d\n\n",
emprs.le_fnameStatus == adFldOK ?
emprs.m_sze_fname : "<NULL>",
emprs.le_lnameStatus == adFldOK ?
emprs.m_sze_lname : "<NULL>",
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.month : 0,
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.day : 0,
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.year : 0); // Requery Recordset and reset the hire date.
pRstEmployee->Requery(adOptionUnspecified);
// Open an IADORecordBinding interface pointer which we'll
// use for Binding Recordset to a class.
TESTHR(pRstEmployee->QueryInterface(
__uuidof(IADORecordBinding),(LPVOID*)&picRs)); // Rebind the Recordset to a C++ Class here.
TESTHR(picRs->BindToRecordset(&emprs));
emprs.m_sze_hiredate = varDate;
picRs->Update(&emprs);
printf("\nData after reset\n");
printf("\tName - Hire Date\n");
printf(" %s %s - %d/%d/%d",emprs.le_fnameStatus == adFldOK ?
emprs.m_sze_fname : "<NULL>",
emprs.le_lnameStatus == adFldOK ?
emprs.m_sze_lname : "<NULL>",
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.month : 0,
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.day : 0,
emprs.le_hiredateStatus == adFldOK ?
emprs.m_sze_hiredate.year : 0);
}
catch(_com_error &e)
{
// Notify the user of errors if any.
// Pass a connection pointer accessed from the Connection.
PrintProviderError(pConnection);
PrintComError(e);
} // Clean up objects before exit.
if (pRstEmployee)
if (pRstEmployee->State == adStateOpen)
pRstEmployee->Close();
if (pConnection)
if (pConnection->State == adStateOpen)
pConnection->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.
for(long i = 0;i < nCount;i++)
{
pErr = pConnection->Errors->GetItem(i);
printf("\t Error number: %x\t%s", pErr->Number,
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);
}
// EndOpenCppOpenX.h:// BeginOpenH
#include "icrsint.h"// This Class extracts only fname,lastname and
// hire_date from employee table
class CEmployeeRs : public CADORecordBinding
{BEGIN_ADO_BINDING(CEmployeeRs)
// Column fname is the 2nd field in the table
ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_sze_fname,
sizeof(m_sze_fname), le_fnameStatus, FALSE)
// Column lname is the 4th field in the table.
ADO_VARIABLE_LENGTH_ENTRY2(4, adVarChar, m_sze_lname,
sizeof(m_sze_lname), le_lnameStatus, FALSE) // Column hiredate is the 8th field in the table.
ADO_VARIABLE_LENGTH_ENTRY2(8, adDBDate,m_sze_hiredate,
sizeof(m_sze_hiredate), le_hiredateStatus, TRUE)
END_ADO_BINDING()public:
CHAR m_sze_fname[21];
ULONG le_fnameStatus;
CHAR m_sze_lname[31];
ULONG le_lnameStatus;
DBDATE m_sze_hiredate;
ULONG le_hiredateStatus;
};
// EndOpenH
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