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Fetch Columns Using IRow::GetColumns (or IRow::Open) and ISequentialStream

Large data can be bound or retrieved using the ISequentialStream interface. For bound columns, the status flag DBSTATUS_S_TRUNCATED indicates that the data is truncated.

Security note Security Note

When possible, use Windows Authentication. If Windows Authentication is not available, prompt users to enter their credentials at run time. Avoid storing credentials in a file. If you must persist credentials, you should encrypt them with the Win32 crypto API.

To fetch columns using IRow::GetColumns (or IRow::Open) and ISequentialStream

  1. Establish a connection to the data source.

  2. Execute the command (in this example, ICommandExecute::Execute() is called with IID_IRow).

  3. Fetch the column data using IRow::Open() or IRow::GetColumns().

    • IRow::Open() can be used to open an ISequentialStream on the row. Specify DBGUID_STREAM to indicate that the column contains a stream of binary data (IStream or ISequentialStream can then be used to read the data from the column).

    • If IRow::GetColumns() is used, the pData element of DBCOLUMNACCESS structure is set to point to a stream object.

  4. Use ISequentialStream::Read() repeatedly to read the specified number of bytes into the consumer buffer.

Example

This example shows how to fetch a single row using IRow. In this example one column at a time is retrieved from the row. This example illustrate the use of IRow::Open() as well as IRow::GetColumns(). To read the column data, the example uses ISequentialStream::Read.

This sample requires the AdventureWorks sample database, which you can download from the Microsoft SQL Server Samples and Community Projects home page.

The first (Transact-SQL) code listing creates a table used by the sample.

Compile with ole32.lib oleaut32.lib and execute the second (C++) code listing. This application connects to your computer's default SQL Server instance. On some Windows operating systems, you will need to change (localhost) or (local) to the name of your SQL Server instance. To connect to a named instance, change the connection string from L"(local)" to L"(local)\\name" , where name is the named instance. By default, SQL Server Express installs to a named instance. Make sure your INCLUDE environment variable includes the directory that contains sqlncli.h.

The third (Transact-SQL) code listing deletes the table used by the sample.

USE AdventureWorks
GO

IF EXISTS (SELECT name FROM sysobjects WHERE name = 'MyTable')
     DROP TABLE MyTable
GO

CREATE TABLE MyTable
(
     col1  int,
     col2  varchar(50),
     col3  char(50),
     col4  datetime,
     col5  float,
     col6  money,
     col7  sql_variant,
     col8  binary(50),
     col9  text,
     col10 image
)
GO

-- Enter data
INSERT INTO MyTable
values
(
     10,
     'abcdefghijklmnopqrstuvwxyz',
     'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
     '11/1/1999 11:52 AM',
     3.14,
     99.95,
     CONVERT(nchar(50), N'AbCdEfGhIjKlMnOpQrStUvWxYz'),
     0x123456789,
     REPLICATE('AAAAABBBBB', 500),
     REPLICATE(0x123456789, 500)
)
GO

// compile with: ole32.lib oleaut32.lib
#define DBINITCONSTANTS
#define INITGUID
#define OLEDBVER 0x0250   // to include correct interfaces

#include <stdio.h>
#include <windows.h>
#include <iostream>
#include <oledb.h>
#include <sqlncli.h>

using namespace std;

const int kMaxBuff = 50;
int InitializeAndEstablishConnection();
HRESULT GetColumnSize(IRow* pUnkRow, ULONG iCol);
ULONG PrintData(ULONG iCols, ULONG iStart, DBCOLUMNINFO* prgInfo, DBCOLUMNACCESS* prgColumns);
HRESULT GetColumns(IRow* pUnkRow, ULONG iStart, ULONG iEnd);
HRESULT GetSequentialColumn(IRow* pUnkRow, ULONG iCol, BOOL fOpen = TRUE);

IDBInitialize*       pIDBInitialize     = NULL;
IDBProperties*       pIDBProperties     = NULL;
IDBCreateSession*    pIDBCreateSession  = NULL;
IDBCreateCommand*    pIDBCreateCommand  = NULL;
ICommandText*        pICommandText      = NULL;
IRow*                pIRow              = NULL;
DBCOLUMNINFO*        pDBColumnInfo      = NULL;
IAccessor*           pIAccessor         = NULL;
DBPROP               InitProperties[4];
DBPROPSET            rgInitPropSet[1];
ULONG                i, j;
HRESULT              hresult;
DBROWCOUNT           cNumRows = 0;
ULONG                lNumCols;
WCHAR*               pStringsBuffer;
DBBINDING*           pBindings;
ULONG                ConsumerBufColOffset = 0;
HACCESSOR            hAccessor;
ULONG                lNumRowsRetrieved;
HROW                 hRows[10];
HROW*                pRows = &hRows[0];

int main() {
   ULONG iidx = 0;
   WCHAR* wCmdString = OLESTR("SELECT * FROM MyTable ");  

   // Call a function to initialize and establish connection. 
   if (InitializeAndEstablishConnection() == -1) {
      cout << "Failed to initialize and establish connection.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   // Create a session object.
   if (FAILED(pIDBInitialize->QueryInterface( IID_IDBCreateSession, (void**) &pIDBCreateSession))) {
      cout << "Failed to obtain IDBCreateSession interface.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   if (FAILED(pIDBCreateSession->CreateSession( NULL,
                                                IID_IDBCreateCommand,
                                                (IUnknown**) &pIDBCreateCommand))) {
      cout << "pIDBCreateSession->CreateSession failed.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   // Access the ICommandText interface.
   if (FAILED(pIDBCreateCommand->CreateCommand( NULL, IID_ICommandText, (IUnknown**) &pICommandText))) {
      cout << "Failed to access ICommand interface.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   // Use SetCommandText() to specify the command text.
   if (FAILED(pICommandText->SetCommandText(DBGUID_DBSQL, wCmdString))) {
      cout << "Failed to set command text.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   // Execute the command.
   if (FAILED(hresult = pICommandText->Execute( NULL, IID_IRow, NULL, &cNumRows, (IUnknown **) &pIRow))) {
      cout << "Failed to execute command.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   DBORDINAL cColumns = 0;
   DBCOLUMNINFO* prgInfo = 0;
   OLECHAR* pColNames;

   // Get column count
   HRESULT hr;
   IColumnsInfo* pIColumnsInfo;
   hr = pIRow->QueryInterface(IID_IColumnsInfo, (void**) &pIColumnsInfo);
   if (FAILED(hr))
      goto CLEANUP;
 
   hr = pIColumnsInfo->GetColumnInfo(&cColumns, &prgInfo, &pColNames);
   if (FAILED(hr))
      goto CLEANUP;

   // Get columns (one at a time) using ISequentialStream and Open
   // 3rd parameter is by default TRUE indicating use of ISequentialStream and Open.
   DBCOLUMNINFO* colInfo; 
   for ( iidx = 1 ; iidx <= cColumns ; iidx++ ) {
  colInfo = (DBCOLUMNINFO*)(prgInfo + (iidx - 1));
  if (colInfo->dwFlags & DBCOLUMNFLAGS_ISLONG)
  hresult = GetSequentialColumn(pIRow, iidx);
  else
  hresult = GetColumns(pIRow, iidx, iidx);
   }

   // Release the Row object.
   pIRow->Release();

   // Execute the command again.
   if (FAILED(hresult = pICommandText->Execute(NULL,
                                               IID_IRow,
                                               NULL,
                                               &cNumRows,
                                               (IUnknown **) &pIRow))) {
      cout << "Failed to execute command.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   // Now get columns (one at a time) using ISequentialStream and GetColumns. 
   // The 3rd parameter is by default TRUE indicating use of ISequentialStream 
   // and GetColumns
   for ( iidx = 1 ; iidx <= cColumns ; iidx++ ) {
  colInfo = (DBCOLUMNINFO*)(prgInfo + (iidx - 1));
  if (colInfo->dwFlags & DBCOLUMNFLAGS_ISLONG)
  hresult = GetSequentialColumn(pIRow, iidx, FALSE);
  else
  hresult = GetColumns(pIRow, iidx, iidx);
   }

CLEANUP:
   // Release memory.
   pICommandText->Release();
   pIDBCreateCommand->Release();
   pIDBCreateSession->Release();

   if (FAILED(pIDBInitialize->Uninitialize())) {
      // Uninitialize not required, but it fails if an interface has not been released, can be used for debugging. 
      // cout << "Problem uninitializing.\n";
   }

   pIDBInitialize->Release();

   CoTaskMemFree(prgInfo);
   CoTaskMemFree(pColNames);
   if( pIColumnsInfo )
      pIColumnsInfo->Release();

   // Release the COM library.
   CoUninitialize();
}

HRESULT GetSequentialColumn(IRow* pUnkRow, ULONG iCol, BOOL fOpen) {
   HRESULT hr = NOERROR;
   ULONG cbRead = 0;
   ULONG cbTotal = 0;
   DBORDINAL cColumns = 0;
   ULONG cReads = 0;
   ISequentialStream* pIStream = NULL;
   WCHAR* pBuffer[kMaxBuff];   // 50 chars read by ISequentialStream::Read()
   DBCOLUMNINFO* prgInfo = 0;
   OLECHAR* pColNames = 0;
   IColumnsInfo* pIColumnsInfo;
   DBID columnid;
   DBCOLUMNACCESS column;

   wprintf(L"[RETRIEVING COLUMN %d SEQUENTIALLY]\n", iCol);

   // Get column information (basically get column id).
   hr = pUnkRow->QueryInterface(IID_IColumnsInfo, (void**) &pIColumnsInfo);
   if (FAILED(hr))
      goto CLEANUP;

   hr = pIColumnsInfo->GetColumnInfo(&cColumns, &prgInfo, &pColNames);
   if (FAILED(hr))
      goto CLEANUP;

   // Get Column ID.
   columnid = (prgInfo + (iCol - 1))->columnid;
   if (fOpen) {   // Get columns using ISequentialStream and IRow::Open
      wprintf(L"[RETRIEVING COLUMNS USING ");
      wprintf(L" ISequentialSteam and Open]\n");

      // Open sequential stream.
      hr = pUnkRow->Open(NULL,
                         &columnid,
                         DBGUID_STREAM,
                         0,
                         IID_ISequentialStream,
                         (LPUNKNOWN *)&pIStream);

      if (FAILED(hr)) {
         wprintf(L"Unable to get ISequentialStream interface.\n");
         goto CLEANUP;
      }
   }

   else {   // Get Columns using IRow::GetColumns and ISequentialStream.
      wprintf(L"[RETRIEVING COLUMNS USING ");
      wprintf(L" GetColumns and ISequentialStream]\n");

  IUnknown* pUnkStream = NULL;

      ZeroMemory(&column, sizeof(column));
      column.columnid = prgInfo[iCol - 1].columnid;
      column.wType = DBTYPE_IUNKNOWN;
      column.pData = (LPVOID*) &pUnkStream;

      hr = pUnkRow->GetColumns(1, &column);
      if (FAILED(hr)) {
         wprintf(L"Error executing IRow::GetColumns.\n");
         goto CLEANUP;
      }

      hr = pUnkStream->QueryInterface(IID_ISequentialStream, (LPVOID*) &pIStream);
      if (FAILED(hr)) {
         wprintf(L"Unable to get ISequentialStream interface ");
         wprintf(L"via IRow::GetColumns.\n");
         goto CLEANUP;
      }

      pUnkStream->Release();
   }

   ZeroMemory(pBuffer, kMaxBuff * sizeof(WCHAR));

   // Read 50 chars at a time until no more data.
   do {
      hr = pIStream->Read(pBuffer, kMaxBuff, &cbRead);
      if (FAILED(hr)) {
         wprintf(L"Error reading data.\n");
         goto CLEANUP;
      }

      cbTotal = cbTotal + cbRead;

      // Print the data
      wprintf(L"READ #%d: %-*S\n", ++cReads, kMaxBuff, pBuffer);
   } while(cbRead > 0);

   wprintf(L"[READ %d bytes for column %d.\n", cbTotal, iCol);

CLEANUP:
   if (pIColumnsInfo)
      pIColumnsInfo->Release();

   CoTaskMemFree(prgInfo);
   CoTaskMemFree(pColNames);

   if (pIStream)
      pIStream->Release();

   return hr;
}

BOOL InitColumn(DBCOLUMNACCESS* pCol, DBCOLUMNINFO* pInfo) {
   // If maximum possible length of a value column is very large (text or image
   //  column is read) limit that size to 512 bytes (for illustration purposes).

   ULONG ulSize;
   if (pInfo->wType == DBTYPE_WSTR || pInfo->wType == DBTYPE_STR)
      ulSize = (pInfo->ulColumnSize < 0x7fffffff) ? pInfo->ulColumnSize : 512;
   else
      ulSize = 128; //default buffer to handle conversion to text of non-string data types

   // Verify data buffer is large enough.
   if (pCol->cbMaxLen < (ulSize + 1)) {
      if (pCol->pData) {
         delete [] pCol->pData;
         pCol->pData = NULL;
      }

      // Allocate data buffer
      void * p = pCol->pData = new WCHAR[ulSize + 1];
      if (!(p /*pCol->pData = new WCHAR[ulSize + 1]*/ ))
         return FALSE;

      // set the max length of caller-initialized memory.
      pCol->cbMaxLen = sizeof(WCHAR) * (ulSize + 1);

      // In the above 2 steps, pData is pointing to memory (it is not NULL) and 
      // cbMaxLen has a value (not 0), so next call to IRow->GetData() 
      // will read the data from the column.
   }

   // Clear memory buffer
   ZeroMemory((void*) pCol->pData, pCol->cbMaxLen);

   // Set properties.
   //pCol->wType = DBTYPE_WSTR;
   pCol->wType = DBTYPE_WSTR;
   pCol->columnid = pInfo->columnid;
   pCol->cbDataLen = 0;
   pCol->dwStatus = 0;
   pCol->dwReserved = 0;
   pCol->bPrecision = 0;
   pCol->bScale = 0;

   return TRUE;
}

HRESULT GetColumns(IRow* pUnkRow, ULONG iStart, ULONG iEnd) {
// Start and end are same. Thus, get only one column.
   HRESULT          hr = E_FAIL;
   ULONG            iidx;          // loop counter
   DBORDINAL        cColumns;      // Count of columns
   ULONG            cUserCols;     // Count of user columns
   DBCOLUMNINFO*    prgInfo;       // Column of info. array
   OLECHAR*         pColNames;     // Array of column names
   DBCOLUMNACCESS*  prgColumns;    // Ptr to column access structures array
   DBCOLUMNINFO*    pCurrInfo;
   DBCOLUMNACCESS*  pCurrCol;

   IColumnsInfo* pIColumnsInfo = NULL;

   // Initialize
   cColumns    = 0;
   prgInfo     = NULL;
   pColNames   = NULL;
   prgColumns  = NULL;

   printf("Retrieving data with GetColumns\n");

   // Get column info to build column access array
   hr = pUnkRow->QueryInterface(IID_IColumnsInfo, (void**)&pIColumnsInfo);

   if (FAILED(hr))
      goto CLEANUP;

   hr = pIColumnsInfo->GetColumnInfo(&cColumns, &prgInfo, &pColNames);

   if (FAILED(hr))
      goto CLEANUP;

   // Determine no. of columns to retrieve.  Since iEnd and iStart is same, 
   // this is redundent step.  cUserCols will always be 1.
   cUserCols = iEnd - iStart + 1; 

   // Walk list of columns and setup a DBCOLUMNACCESS structure
   DBCOLUMNACCESS * x = (prgColumns = new DBCOLUMNACCESS[cUserCols]);
   if (!(x /*prgColumns = new DBCOLUMNACCESS[cUserCols]*/ )) {   // cUserCols is only 1
      hr = E_FAIL;
      goto CLEANUP;
   }

   ZeroMemory((void*) prgColumns, sizeof(DBCOLUMNACCESS) * cUserCols);

   for ( iidx = 0 ; iidx < cUserCols ; iidx++ ) {
      pCurrInfo = prgInfo + iidx + iStart - 1;
      pCurrCol = prgColumns + iidx;

      // Here the values of pData and cbMaxLen elements of DBCOLUMNACCESS 
      // elements is set. Thus IRow->GetColumns() will return actual data.
      if ( InitColumn(pCurrCol, pCurrInfo) == FALSE )
         goto CLEANUP;
   }

   hr = pUnkRow->GetColumns(cUserCols, prgColumns);   // cUserCols = 1
   if (FAILED(hr))
      printf("Error occured\n");

   // Show data.
   PrintData(cUserCols, iStart, prgInfo, prgColumns);

CLEANUP:
   if (pIColumnsInfo)
      pIColumnsInfo->Release();
   if (prgColumns)
      delete [] prgColumns;

   return hr;
}
// This function returns the actual width of the data in the column (not the 
// columnwidth in DBCOLUMNFO structure which is the width of the column)
HRESULT GetColumnSize(IRow* pUnkRow, ULONG iCol) {
   HRESULT         hr = NOERROR;
   DBORDINAL       cColumns = 0;   // Count the columns
   DBCOLUMNINFO*   prgInfo;        // Column info array
   OLECHAR*        pColNames;
   DBCOLUMNACCESS  column;          
   DBCOLUMNINFO*   pCurrInfo;
   IColumnsInfo*   pIColumnsInfo = NULL;

   // Initialize
   prgInfo = NULL;
   pColNames = NULL;

   printf("Checking column size\n");

   // Get column info to build column access array
   hr = pUnkRow->QueryInterface(IID_IColumnsInfo, (void**) &pIColumnsInfo);
   if (FAILED(hr))
      goto CLEANUP;

   hr = pIColumnsInfo->GetColumnInfo(&cColumns, &prgInfo, &pColNames);
   if (FAILED(hr))
      goto CLEANUP;
   printf("Value of cColumns is %d\n", cColumns);

   // Setup a DBCOLUMNACCESS structure: pData is set to NULL and cbMaxLen is set 
   // to 0. Thus IRow->GetColumns() returns only the actual column length in
   // cbDataLen member of DBCOLUMNACCESS structure.In this case you can call 
   // IRow->GetColumns() again for the same column to retrieve actual data in the second call.
   ZeroMemory((void*) &column, sizeof(DBCOLUMNACCESS));
   column.pData = NULL;

   pCurrInfo = prgInfo + iCol - 1;
   // Get column id in DBCOLUMNACCESS structure. It is then used in GetColumn().
   column.columnid = pCurrInfo->columnid; 

   printf("column.columnid value is %d\n", column.columnid);
   // We know which column to get.  The column.columnid gives the column number.
   hr = pUnkRow->GetColumns(1, &column); 
   if (FAILED(hr))
      printf("Errors occured\n");

   // Show data
   PrintData(1, iCol, prgInfo, &column);

CLEANUP:
   if (pIColumnsInfo)
      pIColumnsInfo->Release();
   return hr;
}

BOOL GetStatus(DWORD dwStatus, WCHAR* pwszStatus) {
   switch (dwStatus) {
   case DBSTATUS_S_OK:
      wcscpy_s(pwszStatus, 255, L"DBSTATUS_S_OK");
      break;
   case DBSTATUS_E_CANTCONVERTVALUE:
   wcscpy_s(pwszStatus, 255, L"DBSTATUS_E_CANTCONVERTVALUE");
   break;
   case DBSTATUS_S_ISNULL:
   wcscpy_s(pwszStatus, 255, L"DBSTATUS_S_ISNULL");
   break;
   case DBSTATUS_E_UNAVAILABLE:
      wcscpy_s(pwszStatus, 255, L"DBSTATUS_E_UNAVAILABLE");
      break;
   case DBSTATUS_S_TRUNCATED:
      wcscpy_s(pwszStatus, 255, L"DBSTATUS_S_TRUNCATED");
      break;
   default:
      swprintf_s(pwszStatus, sizeof(pwszStatus), L"OTHER STATUS VALUE: %d", dwStatus);
   }
   return TRUE;
}

ULONG PrintData(ULONG iCols, 
                ULONG iStart, 
                DBCOLUMNINFO* prgInfo, 
                DBCOLUMNACCESS* prgColumns) {

   WCHAR wszStatus[255];
   DBCOLUMNINFO* pCurrInfo;
   DBCOLUMNACCESS* pCurrCol;
   ULONG iidx = 0;       // Loop counter

   printf("%-3s %-20s %-21s %-9s %-9s %-50s\n", "No.", "Name", "Status", "Length", "Max", "Data");

   for ( iidx = 0 ; iidx < iCols ; iidx++ ) {
      pCurrInfo = prgInfo + iidx + iStart - 1;
      pCurrCol = prgColumns + iidx;

      GetStatus(pCurrCol->dwStatus, wszStatus); 
      // was the data successfully retrieved?
      wprintf(L"%-3d %-20s %-21s %-9d %-9d %-50s\n", iStart + iidx,
                                                    pCurrInfo->pwszName,
                                                    wszStatus,
                                                    pCurrCol->cbDataLen,
                                                    pCurrCol->cbMaxLen,
pCurrCol->dwStatus == DBSTATUS_S_ISNULL ? L"(NULL)" : (WCHAR*) pCurrCol->pData);
   }

   wprintf(L"\n");
   return iidx;
}

int InitializeAndEstablishConnection() {    
   // Initialize the COM library.
   CoInitialize(NULL);

   // Obtain access to the SQLNCLI provider.
   hresult = CoCreateInstance(CLSID_SQLNCLI11, 
                              NULL, 
                              CLSCTX_INPROC_SERVER,
                              IID_IDBInitialize, 
                              (void **) &pIDBInitialize);

   if(FAILED(hresult)) {
      printf("Failed to get IDBInitialize interface.\n");
      // Insert your code for cleanup and error handling
      return -1;
   }

   // Initialize the property values needed to establish the connection.
   for (i =  0 ; i < 4 ; i++ )
      VariantInit(&InitProperties[i].vValue);

   // Server name.
   InitProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
   InitProperties[0].vValue.vt = VT_BSTR;

   InitProperties[0].vValue.bstrVal = SysAllocString(L"(local)");
   InitProperties[0].dwOptions     = DBPROPOPTIONS_REQUIRED;
   InitProperties[0].colid         = DB_NULLID;

   // Database.
   InitProperties[1].dwPropertyID  = DBPROP_INIT_CATALOG;
   InitProperties[1].vValue.vt     = VT_BSTR;
   InitProperties[1].vValue.bstrVal= SysAllocString(L"AdventureWorks");
   InitProperties[1].dwOptions     = DBPROPOPTIONS_REQUIRED;
   InitProperties[1].colid         = DB_NULLID;

   // connection
   InitProperties[2].dwPropertyID  = DBPROP_AUTH_INTEGRATED;
   InitProperties[2].vValue.vt     = VT_BSTR;
   InitProperties[2].vValue.bstrVal= SysAllocString(L"SSPI");
   InitProperties[2].dwOptions     = DBPROPOPTIONS_REQUIRED;
   InitProperties[2].colid         = DB_NULLID;

   // Now that the properties are set, construct the DBPROPSET structure
   // (rgInitPropSet). The DBPROPSET structure is used to pass an array 
   // of DBPROP structures (InitProperties) to the SetProperties method.
   rgInitPropSet[0].guidPropertySet = DBPROPSET_DBINIT;
   rgInitPropSet[0].cProperties    = 4;
   rgInitPropSet[0].rgProperties   = InitProperties;

   // Set initialization properties.
   hresult = pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);
   if (FAILED(hresult)) {
      cout << "Failed to get IDBProperties interface.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   hresult = pIDBProperties->SetProperties(1, rgInitPropSet); 
   if (FAILED(hresult)) {
      cout << "Failed to set initialization properties.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   pIDBProperties->Release();

   // Now establish the connection to the data source.
   if (FAILED(pIDBInitialize->Initialize())) {
      cout << "Problem establishing connection to the data source.\n";
      // Insert your code for cleanup and error handling
      return -1;
   }

   return 0;
}

USE AdventureWorks
GO

IF EXISTS (SELECT name FROM sysobjects WHERE name = 'MyTable')
     DROP TABLE MyTable
GO

See Also

Other Resources

OLE DB How-to Topics