The GetRowsEx method retrieves multiple records and enables you to specify the data types of the fields stored in your application variables. It has the following parameters.
| Parameter | Data type | Description |
| pvBuffer | LPVOID | Pointer to the buffer in which to store returned records. |
| CbRow | LONG | Length of the record, in bytes. |
| Prb | LPDAORSETBINDING | Pointer to the binding structure (see the following description). |
| Cbinding | LONG | Number of bindings. |
| PvVarBuffer | LPVOID | Pointer to the buffer in which to store variable-length data. |
| CbVarBuffer | LONG | Length, in bytes, of pvVarBuffer. |
| Lrows | LONG | Number of records requested. |
The DAORSETBINDING structure specifies how data is to be copied from the records to the memory buffer. A separate binding structure must be filled in for each field retrieved. DAORSETBINDING is defined as follows:
typedef struct
{
DWORD dwBindIndexType;
union
{
LONG i;
LPCTSTR pstr;
};
DWORD dwType;
DWORD dwOffset;
DWORD cb;
} DAORSETBINDING, *LPDAORSETBINDING;
The DAORSETBINDING structure has the following members.
| Member | Description |
| dwBindIndexType |
Value specifying whether a field is indicated by an index number or by name. This member is one of the following values:
dbBindIndexINT (index) |
| dwType |
Data type. This member is one of the following values:
dbBindI2 (long) |
| dwOffset | Offset, in bytes, in the record buffer where the data is copied. |
| Cb | Field length, in bytes. |
The following code from the GetRows example shows how to use the GetRowsEx method. Note that the table schema is known a priori, allowing you to predefine a structure for the data.
Two different binding schemes for retrieving string data are shown. If the size of the string is fixed, you can retrieve the strings directly into the structure. If you are using variable-length strings, they will be placed sequentially in a single large buffer, and a pointer into that buffer will be stored in the structure.
// Structure for GetRowsEx:
typedef struct
{
LONG lEmpId;
TCHAR *strLastName;
TCHAR strFirstName[20];
} EMP, *LPEMP ;
// Employee table binding:
DAORSETBINDING Bindings[] =
{
//Index Type Column Type Offset Size
{dbBindIndexINT, EMP_ID, dbBindI4, offsetof(EMP,lEmpId), sizeof(LONG)},
{dbBindIndexINT, EMP_LNAME, dbBindLPSTRING, offsetof(EMP,strLastName), sizeof(TCHAR *)},
{dbBindIndexINT, EMP_FNAME, dbBindSTRING, offsetof(EMP,strFirstName), sizeof(TCHAR) * 20}
};
// Perform C++ GetRowsEx against the Employee table.
void CGetRowsDlg::DoGetRowsEx()
{
LPEMP pEmpRows = new EMP[MAX_EMP_REC];
CListBox *pListBox = (CListBox *)GetDlgItem(IDD_GETROWSLISTEX);
CString strLBRow;
TCHAR szId[16];
LONG lNumRecords;
LONG lCount;
TCHAR pBuf[MAX_EMP_REC * 15]; // Allow average of 15 chars/name.
//Perform GetRows on Employee table.
//This GetRows uses a specific C++ structure.
try
{
lNumRecords = m_cEmpRecordSet.GetRowsEx(pEmpRows, sizeof(EMP),
&Bindings[0], sizeof(Bindings) / sizeof(DAORSETBINDING),
pBuf, sizeof(pBuf),
MAX_EMP_REC); //arbitrarily get MAX_EMP_REC rows
}
catch (CdbException e)
{
//Differentiate between GetRowsEx Errors and other CdbExceptions.
//See defines in DAOGETRW.H.
if( e.m_hr == E_ROWTOOSHORT ||
e.m_hr == E_BADBINDINFO ||
e.m_hr == E_COLUMNUNAVAILABLE )
{
AfxMessageBox(_T("Error in GetRowsEx call."));
}
else
{
AfxMessageBox(_T("General CdbException"));
}
delete [] pEmpRows;
return;
}
//Step through the returned rows.
for (lCount = 0; lCount < lNumRecords; lCount++)
{
strLBRow.Empty();
wsprintf(szId, _T("%d, "), pEmpRows[lCount].lEmpId);
strLBRow += szId;
strLBRow += pEmpRows[lCount].strLastName;
strLBRow += _T(", ");
strLBRow += (LPCTSTR) pEmpRows[lCount].strFirstName;
pListBox->AddString(strLBRow);
}
delete [] pEmpRows;
}