Delete Method Example (VC++)
This example uses the Delete method to remove a specified record from a Recordset.
#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 "DeleteX.h"
//Function Declarations.
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void DeleteX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
///////////////////////////////////////////////////////////
// //
// Main Function //
// //
///////////////////////////////////////////////////////////
void main()
{
if(FAILED(::CoInitialize(NULL)))
return;
DeleteX();
::CoUninitialize();
}
///////////////////////////////////////////////////////////
// //
// DeleteX Function //
// //
///////////////////////////////////////////////////////////
void DeleteX(void)
{
// Define ADO object pointers.
// Initialize pointers on define.
// These are in the ADODB:: namespace.
_RecordsetPtr pRstRoySched = NULL;
// Define Other Variables
IADORecordBinding *picRs = NULL; //Interface Pointer declared.
CRoySchedRs royschrs; //C++ class object
HRESULT hr = S_OK;
char strTitleID[10], strTmpTitleID[10]="";
long longHiRange;
int intRoyalty, intLoRange, cnt=0;
bool blnFound = TRUE;
_bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
"Initial Catalog=Pubs;User Id=sa;Password=;");
try
{
// Open RoySched table
TESTHR(pRstRoySched.CreateInstance(__uuidof(Recordset)));
pRstRoySched->CursorLocation = adUseClient;
pRstRoySched->CursorType = adOpenStatic;
pRstRoySched->LockType = adLockBatchOptimistic;
TESTHR(pRstRoySched->Open("SELECT * FROM roysched WHERE”
“ royalty = 20",strCnn,adOpenStatic,adLockBatchOptimistic,
adCmdText));
// Prompt for a record to delete.
printf("Before delete there are %d Titles with 20 percent "
"royalty :\n", pRstRoySched->RecordCount);
// Open an IADORecordBinding interface pointer which we'll use
// for Binding Recordset to a class.
TESTHR(pRstRoySched->QueryInterface(
__uuidof(IADORecordBinding),(LPVOID*)&picRs));
// Bind the Recordset to a C++ Class here
TESTHR(picRs->BindToRecordset(&royschrs));
while(!(pRstRoySched->EndOfFile))
{
printf("%s\n", royschrs.lemp_titleidStatus == adFldOK ?
royschrs.m_sz_titleid : "<NULL>");
pRstRoySched->MoveNext();
}
printf("\nEnter the ID of a record to delete: ");
gets(strTitleID);
// Converting the title_id to upper case
for( cnt=0; cnt<10; cnt++)
{
if(strTitleID[cnt] != NULL)
{
if( IsCharAlpha( strTitleID[cnt]) )
{
if( islower( strTitleID[cnt]) )
strTmpTitleID[cnt] = _toupper(strTitleID[cnt]);
else
strTmpTitleID[cnt] = strTitleID[cnt];
}
else
{
strTmpTitleID[cnt] = strTitleID[cnt];
}
}
}
// Move to the record and save data so it can be restored.
pRstRoySched->PutFilter ("title_id = '" +
(_bstr_t)(LPCSTR)strTmpTitleID + "'");
if(pRstRoySched->RecordCount != 0)
{
intLoRange = royschrs.m_sz_lorange;
longHiRange = royschrs.m_sz_hirange;
intRoyalty = royschrs.m_sz_royalty;
// Delete the record
pRstRoySched->Delete(adAffectCurrent);
pRstRoySched->UpdateBatch(adAffectCurrent);
}
else
{
blnFound = FALSE;
printf("This Title ID not available");
}
// Show the results.
VARIANT varFilter;
varFilter.vt = VT_I2;
varFilter.iVal = adFilterNone;
pRstRoySched->PutFilter (varFilter);
pRstRoySched->Requery(-1);
// Bind the Recordset to a C++ Class here.TESTHR(picRs->BindToRecordset(&royschrs));
printf("\nAfter delete there are %d Titles with 20 percent"
" royalty: ", pRstRoySched->RecordCount);
while(!(pRstRoySched->EndOfFile))
{
printf("\n%s", royschrs.lemp_titleidStatus == adFldOK ?
royschrs.m_sz_titleid : "<NULL>");
pRstRoySched->MoveNext();
}
// Restore the data because this is a demonstration.
if(blnFound)
{
strcpy((char*)royschrs.m_sz_titleid,
(const char*) strTmpTitleID);
royschrs.m_sz_lorange = intLoRange;
royschrs.m_sz_hirange = longHiRange;
royschrs.m_sz_royalty = intRoyalty;
TESTHR(picRs->AddNew(&royschrs));
pRstRoySched->UpdateBatch(adAffectCurrent);
}
// Clean up objects before exit.
pRstRoySched->Close();
// Release the IADORecordset Interface here
if (picRs)
picRs->Release();
}
catch(_com_error &e)
{
// Notify the user of errors if any.
// Pass a connection pointer accessed from the Recordset.
_variant_t vtConnect = pRstRoySched->GetActiveConnection();
// GetActiveConnection returns connect string if connection
// is not open, else returns Connection object.
switch(vtConnect.vt)
{
case VT_BSTR:
PrintComError(e);
break;
case VT_DISPATCH:
PrintProviderError(vtConnect);
break;
default:
printf("Errors occured.");
break;
}
}
}
///////////////////////////////////////////////////////////
// //
// 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("Error number: %x\t%s\n", 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);
}
DeleteX.h:
#include "icrsint.h"
// This Class extracts titleid, lorange, hirange and royalty
// from the "roysched" table.
class CRoySchedRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CRoySchedRs)
//Column empid is the 1st field in the recordset
ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_sz_titleid,
sizeof(m_sz_titleid), lemp_titleidStatus, TRUE)
ADO_VARIABLE_LENGTH_ENTRY2(2, adInteger, m_sz_lorange,
sizeof(m_sz_lorange), lemp_lorangeStatus, TRUE)
ADO_VARIABLE_LENGTH_ENTRY2(3, adInteger, m_sz_hirange,
sizeof(m_sz_hirange), lemp_hirangeStatus, TRUE)
ADO_VARIABLE_LENGTH_ENTRY2(4, adInteger, m_sz_royalty,
sizeof(m_sz_royalty), lemp_royaltyStatus, TRUE)
END_ADO_BINDING()
public:
CHAR m_sz_titleid[10];
ULONG lemp_titleidStatus;
ULONG m_sz_lorange;
ULONG lemp_lorangeStatus;
ULONG m_sz_hirange;
ULONG lemp_hirangeStatus;
ULONG m_sz_royalty;
ULONG lemp_royaltyStatus;
};