Delete 方法範例 (VC++)
這個範例會使用 Delete 方法，從 Recordset 移除指定的記錄。
範例
// DeleteMethodExample.cpp
// compile with: /EHsc /c
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")
#include <stdio.h>
#include <ole2.h>
#include <conio.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;
};
// Function Declarations.
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };
void DeleteX();
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
inline char* mygets(char* strDest, int n) {
char strExBuff[10];
char* pstrRet = fgets(strDest, n, stdin);
if (pstrRet == NULL)
return NULL;
if (!strrchr(strDest, '\n'))
// Exhaust the input buffer.
do {
fgets(strExBuff, sizeof(strExBuff), stdin);
} while (!strrchr(strExBuff, '\n'));
else
// Replace '\n' with '\0'
strDest[strrchr(strDest, '\n') - strDest] = '\0';
return pstrRet;
}
int main() {
if ( FAILED(::CoInitialize(NULL)) )
return -1;
DeleteX();
::CoUninitialize();
}
void DeleteX() {
// 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
char strTitleID[10], strTmpTitleID[10] = "";
long longHiRange = 0;
int intRoyalty = 0, intLoRange = 0, cnt = 0;
bool blnFound = TRUE;
_bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");
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 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: ");
mygets(strTitleID, 10);
// 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 ) {
// Set the final character of the destination string to NULL.
royschrs.m_sz_titleid[sizeof(royschrs.m_sz_titleid) - 1] = '\0';
// The source string will get truncated if its length is
// longer than the length of the destination string minus one.
strncpy_s(royschrs.m_sz_titleid, strTmpTitleID, sizeof(royschrs.m_sz_titleid) - 1);
royschrs.m_sz_lorange = intLoRange;
royschrs.m_sz_hirange = longHiRange;
royschrs.m_sz_royalty = intRoyalty;
TESTHR(picRs->AddNew(&royschrs));
pRstRoySched->UpdateBatch(adAffectCurrent);
}
}
catch(_com_error &e) {
// Display errors, if any. Pass 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 occurred.");
break;
}
}
// Clean up objects before exit. Release the IADORecordset Interface here
if (picRs)
picRs->Release();
if (pRstRoySched)
if (pRstRoySched->State == adStateOpen)
pRstRoySched->Close();
}
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);
}
}
}
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);
}
範例輸入
TC4203
範例輸出
Before delete there are 7 titles with 20 percent royalty :
BU2075
MC3021
TC3218
BU1111
MC2222
TC4203
BU7832
Enter the ID of a record to delete:
After delete there are 6 titles with 20 percent royalty:
BU2075
MC3021
TC3218
BU1111
MC2222
BU7832