Définir des données volumineuses (OLE DB)
S’applique à : 
SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)
Cet exemple montre comment définir des données BLOB, créer une table, ajouter un exemple d’enregistrement, extraire cet enregistrement dans l’ensemble de lignes, puis définir la valeur du champ BLOB. Cet exemple n'est pas pris en charge sur la plateforme IA64.
Pour transmettre un pointeur à son propre objet de stockage, le consommateur crée un accesseur qui lie la valeur de la colonne BLOB, puis appelle les méthodes IRowsetChange::SetData ou IRowsetChange::InsertRow .
Les exemples de code Transact-SQL de cet article sont fondés sur l’échantillon de base de données AdventureWorks2022 ou AdventureWorksDW2022 fourni, que vous pouvez télécharger à partir de la page d’accueil Échantillons et projets communautaires Microsoft SQL Server.
Important
Lorsque c'est possible, utilisez l'authentification Windows. Si l'authentification Windows n'est pas disponible, invitez les utilisateurs à entrer leurs informations d'identification au moment de l'exécution. Évitez de stocker ces informations dans un fichier. Si vous devez rendre les informations d'identification persistantes, chiffrez-les avec l' API de chiffrement Win32.
Procédures
Pour définir des données BLOB
Créez une structure DBOBJECT décrivant la manière dont la colonne BLOB doit être accessible. Définissez l'élément dwFlag de la structure DBOBJECT à STGM_READ, puis définissez l'élément iid sur IID_ISequentialStream (interface à exposer).
Définissez les propriétés du groupe de propriétés DBPROPSET_ROWSET de sorte que l'ensemble de lignes puisse être mis à jour.
Créez un jeu de liaisons (une pour chaque colonne) en utilisant un tableau de structures DBBINDING. Définissez l’élément wType dans la structure DBBINDING sur DBTYPE_IUNKNOWN, puis l’élément pObject de sorte qu’il pointe vers la structure DBOBJECT que vous avez créée.
Créez un accesseur à l'aide des informations de liaison du tableau des structures DBBINDINGS.
Appelez la méthode GetNextRows pour extraire les lignes suivantes dans l'ensemble de lignes. Appelez la méthode GetData pour lire les données de l'ensemble de lignes.
Pour définir les données, créez un objet de stockage contenant les données (ainsi que l'indicateur de longueur), puis appelez IRowsetChange::SetData (ou IRowsetChange::InsertRow) avec l'accesseur qui lie la colonne BLOB.
Exemple
Description
Compilez avec ole32.lib oleaut32.lib et exécutez le code C++ suivant. Cette application vous permet de vous connecter à l'instance de SQL Server par défaut de votre ordinateur. Sur certains systèmes d'exploitation Windows, vous devrez remplacer (localhost) ou (local) par le nom de votre instance SQL Server . Pour vous connecter à une instance nommée, changez la chaîne de connexion L"(local)" en L"(local)\\name", où name correspond à l’instance nommée. Par défaut, SQL Server Express est installé dans une instance nommée. Vérifiez que votre variable d’environnement INCLUDE inclut le répertoire qui contient msoledbsql.h.
Code
// compile with: ole32.lib oleaut32.lib
#define UNICODE
#define DBINITCONSTANTS
#define INITGID
#define OLEDBVER 0x0250 // to include correct interfaces
#include <windows.h>
#include <stdio.h>
#include <stddef.h>
#include <iostream>
#include <oledb.h>
#include <oledberr.h>
#include <msoledbsql.h>
using namespace std;
#define SAFE_RELEASE(pIUnknown) if(pIUnknown) (pIUnknown)->Release();
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown);
HRESULT CreateTable(ICommandText* pICommandText);
class CSeqStream : public ISequentialStream {
public:
// Constructors
CSeqStream();
virtual ~CSeqStream();
virtual BOOL Seek(ULONG iPos);
virtual BOOL Clear();
virtual BOOL CompareData(void* pBuffer);
virtual ULONG Length() { return m_cBufSize; };
virtual operator void* const() { return m_pBuffer; };
STDMETHODIMP_(ULONG) AddRef(void);
STDMETHODIMP_(ULONG) Release(void);
STDMETHODIMP QueryInterface(REFIID riid, LPVOID *ppv);
STDMETHODIMP Read(
/* [out] */ void __RPC_FAR *pv,
/* [in] */ ULONG cb,
/* [out] */ ULONG __RPC_FAR *pcbRead);
STDMETHODIMP Write(
/* [in] */ const void __RPC_FAR *pv,
/* [in] */ ULONG cb,
/* [out]*/ ULONG __RPC_FAR *pcbWritten);
private:
ULONG m_cRef; // reference count
void* m_pBuffer; // buffer
ULONG m_cBufSize; // buffer size
ULONG m_iPos; // current index position in the buffer
};
// class implementation
CSeqStream::CSeqStream() {
m_iPos = 0;
m_cRef = 0;
m_pBuffer = NULL;
m_cBufSize = 0;
// The constructor AddRef's
AddRef();
}
CSeqStream::~CSeqStream() {
// Shouldn't have any references left ASSERT(m_cRef == 0);
CoTaskMemFree(m_pBuffer);
}
ULONG CSeqStream::AddRef() {
return ++m_cRef;
}
ULONG CSeqStream::Release() {
// ASSERT(m_cRef);
if (--m_cRef)
return m_cRef;
delete this;
return 0;
}
HRESULT CSeqStream::QueryInterface(REFIID riid, void** ppv) {
// ASSERT(ppv);
*ppv = NULL;
if (riid == IID_IUnknown)
*ppv = this;
if (riid == IID_ISequentialStream)
*ppv = this;
if(*ppv) {
((IUnknown*)*ppv)->AddRef();
return S_OK;
}
return E_NOINTERFACE;
}
BOOL CSeqStream::Seek(ULONG iPos) {
// Make sure the desired position is within the buffer
// ASSERT(iPos == 0 || iPos < m_cBufSize);
// Reset the current buffer position
m_iPos = iPos;
return TRUE;
}
BOOL CSeqStream::Clear() {
// Frees the buffer
m_iPos = 0;
m_cBufSize = 0;
CoTaskMemFree(m_pBuffer);
m_pBuffer = NULL;
return TRUE;
}
BOOL CSeqStream::CompareData(void* pBuffer) {
// ASSERT(pBuffer);
// Quick and easy way to compare user buffer with the stream
return memcmp(pBuffer, m_pBuffer, m_cBufSize) == 0;
}
HRESULT CSeqStream::Read(void *pv, ULONG cb, ULONG* pcbRead) {
// Parameter checking
if (pcbRead)
*pcbRead = 0;
if (!pv)
return STG_E_INVALIDPOINTER;
if (cb == 0)
return S_OK;
// Actual code
ULONG cBytesLeft = m_cBufSize - m_iPos;
ULONG cBytesRead = cb > cBytesLeft ? cBytesLeft : cb;
// if no more bytes to retrieve return
if (cBytesLeft == 0)
return S_FALSE;
// Copy to users buffer the number of bytes requested or remaining
memcpy(pv, (void*)((BYTE*)m_pBuffer + m_iPos), cBytesRead);
m_iPos += cBytesRead;
if (pcbRead)
*pcbRead = cBytesRead;
if (cb != cBytesRead)
return S_FALSE;
return S_OK;
}
HRESULT CSeqStream::Write(const void *pv, ULONG cb, ULONG* pcbWritten) {
// Parameter checking
if (!pv)
return STG_E_INVALIDPOINTER;
if (pcbWritten)
*pcbWritten = 0;
if (cb == 0)
return S_OK;
// Enlarge the current buffer
m_cBufSize += cb;
// Need to append to the end of the stream
m_pBuffer = CoTaskMemRealloc(m_pBuffer, m_cBufSize);
memcpy((void*)((BYTE*)m_pBuffer + m_iPos), pv, cb);
// m_iPos += cb;
if (pcbWritten)
*pcbWritten = cb;
return S_OK;
}
int main() {
CoInitialize(NULL);
DBOBJECT ObjectStruct;
ObjectStruct.dwFlags = STGM_READ;
ObjectStruct.iid = IID_ISequentialStream;
struct BLOBDATA {
DBSTATUS dwStatus;
DBLENGTH dwLength;
ISequentialStream* pISeqStream;
};
BLOBDATA BLOBGetData;
BLOBDATA BLOBSetData;
const ULONG cBindings = 1;
DBBINDING rgBindings[cBindings];
HRESULT hr = S_OK;
IAccessor* pIAccessor = NULL;
ICommandText* pICommandText = NULL;
ICommandProperties* pICommandProperties = NULL;
IRowsetChange* pIRowsetChange = NULL;
IRowset* pIRowset = NULL;
CSeqStream* pMySeqStream = NULL;
DBCOUNTITEM cRowsObtained = 0;
HACCESSOR hAccessor = DB_NULL_HACCESSOR;
DBBINDSTATUS rgBindStatus[cBindings];
HROW* rghRows = NULL;
const ULONG cPropSets = 1;
DBPROPSET rgPropSets[cPropSets];
const ULONG cProperties = 1;
DBPROP rgProperties[cProperties];
const ULONG cBytes = 10;
BYTE pBuffer[cBytes];
ULONG cBytesRead = 0;
BYTE pReadData[cBytes]; // read BLOB data in this array
memset(pReadData, 0xAA, cBytes);
BYTE pWriteData[cBytes]; // write BLOB data from this array
memset(pWriteData, 'D', cBytes);
// Get Command object
hr = GetCommandObject(IID_ICommandText, (IUnknown**)&pICommandText);
if (FAILED(hr)) {
printf("Failed to get ICommandText interface.\n");
// Release any references and return.
goto Exit;
}
// Create table with image column and index
hr = CreateTable(pICommandText);
if (FAILED(hr)) {
printf("Failed to create table.\n");
// Release any references and return.
goto Exit;
}
// Set the DBPROPSET structure. It is used to pass an array
// of DBPROP structures to SetProperties().
rgPropSets[0].guidPropertySet = DBPROPSET_ROWSET;
rgPropSets[0].cProperties = cProperties;
rgPropSets[0].rgProperties = rgProperties;
// Now set properties in the property group (DBPROPSET_ROWSET)
rgPropSets[0].rgProperties[0].dwPropertyID = DBPROP_UPDATABILITY;
rgPropSets[0].rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
rgPropSets[0].rgProperties[0].dwStatus = DBPROPSTATUS_OK;
rgPropSets[0].rgProperties[0].colid = DB_NULLID;
rgPropSets[0].rgProperties[0].vValue.vt = VT_I4;
V_I4(&rgPropSets[0].rgProperties[0].vValue) = DBPROPVAL_UP_CHANGE;
// Set the rowset properties
hr = pICommandText->QueryInterface(IID_ICommandProperties,
(void **)&pICommandProperties);
if (FAILED(hr)) {
printf("Failed to get ICommandProperties to set rowset properties.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);
if (FAILED(hr)) {
printf("Execute failed to set rowset properties.\n");
// Release any references and return.
goto Exit;
}
// Execute a command (SELECT * FROM TestISeqStream)
hr = pICommandText->SetCommandText(DBGUID_DBSQL, L"SELECT * FROM TestISeqStream");
if (FAILED(hr)) {
printf("Failed to set command text SELECT * FROM.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandText->Execute(NULL,
IID_IRowsetChange,
NULL,
NULL,
(IUnknown**)&pIRowsetChange);
if (FAILED(hr)) {
printf("Failed to execute the command SELECT * FROM.\n");
// Release any references and return.
goto Exit;
}
// Fill the DBBINDINGS array.
rgBindings[0].iOrdinal = 2; // ordinal position
rgBindings[0].obValue = offsetof(BLOBDATA, pISeqStream);
rgBindings[0].obLength = offsetof(BLOBDATA, dwLength);
rgBindings[0].obStatus = offsetof(BLOBDATA, dwStatus);
rgBindings[0].pTypeInfo = NULL;
rgBindings[0].pObject = &ObjectStruct;
rgBindings[0].pBindExt = NULL;
rgBindings[0].dwPart = DBPART_VALUE | DBPART_STATUS | DBPART_LENGTH;
rgBindings[0].dwMemOwner = DBMEMOWNER_CLIENTOWNED;
rgBindings[0].eParamIO = DBPARAMIO_NOTPARAM;
rgBindings[0].cbMaxLen = 0;
rgBindings[0].dwFlags = 0;
rgBindings[0].wType = DBTYPE_IUNKNOWN;
rgBindings[0].bPrecision = 0;
rgBindings[0].bScale = 0;
// Create an accessor using the binding information.
hr = pIRowsetChange->QueryInterface(IID_IAccessor, (void**)&pIAccessor);
if (FAILED(hr)) {
printf("Failed to get IAccessor interface.\n");
// Release any references and return.
goto Exit;
}
hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,
cBindings,
rgBindings,
sizeof(BLOBDATA),
&hAccessor,
rgBindStatus);
if (FAILED(hr)) {
printf("Failed to create an accessor.\n");
// Release any references and return.
goto Exit;
}
// get the first row.
hr = pIRowsetChange->QueryInterface(IID_IRowset, (void **)&pIRowset);
if (FAILED(hr)) {
printf("Failed to get IRowset interface.\n");
// Release any references and return.
goto Exit;
}
hr = pIRowset->GetNextRows(NULL, 0, 1, &cRowsObtained, &rghRows);
hr = pIRowset->GetData(rghRows[0], hAccessor, &BLOBGetData);
// Verify the retrieved data, only if data is not null.
if (BLOBGetData.dwStatus == DBSTATUS_S_ISNULL) {
// Process null data
printf("Provider returned a null value.\n");
}
else if(BLOBGetData.dwStatus == DBSTATUS_S_OK) {
// Provider returned a nonNULL value
BLOBGetData.pISeqStream->Read( pBuffer, cBytes, &cBytesRead);
if (memcmp(pBuffer, pReadData, cBytes) != 0) {
// cleanup
}
SAFE_RELEASE(BLOBGetData.pISeqStream);
}
// Set up data for SetData.
pMySeqStream = new CSeqStream();
// Put data into ISequentialStream object for the provider to write.
pMySeqStream->Write(pWriteData, cBytes, NULL);
BLOBSetData.pISeqStream = (ISequentialStream*)pMySeqStream;
BLOBSetData.dwStatus = DBSTATUS_S_OK;
BLOBSetData.dwLength = pMySeqStream->Length();
// Set the data.
hr = pIRowsetChange->SetData(rghRows[0], hAccessor, &BLOBSetData);
if (FAILED(hr)) {
printf("Failed to set data.\n");
// Release any references and return.
goto Exit;
}
hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);
if (FAILED(hr)) {
printf("Failed to release accessor.\n");
// Release any references and return.
goto Exit;
}
hr = pIRowset->ReleaseRows(cRowsObtained, rghRows, NULL, NULL, NULL);
if (FAILED(hr)) {
printf("Failed to release rows.\n");
// Release any references and return.
goto Exit;
}
Exit:
// Release all allocated memory and release interface pointers.
CoUninitialize();
}
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown) {
HRESULT hr = S_OK;
// Local interface pointers, until a connection is made.
IDBInitialize* pIDBInitialize = NULL;
IDBProperties* pIDBProperties = NULL;
IDBCreateSession* pIDBCreateSession = NULL;
IDBCreateCommand* pIDBCreateCommand = NULL;
const ULONG cPropSets = 1;
DBPROPSET rgPropSets[cPropSets];
const ULONG cProperties = 4;
DBPROP rgProperties[cProperties];
// Initialize property values needed to establish connection.
for ( ULONG i = 0 ; i < 4 ; i++ )
VariantInit(&rgProperties[i].vValue);
// Server name.
rgProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
rgProperties[0].vValue.vt = VT_BSTR;
rgProperties[0].vValue.bstrVal = SysAllocString(L"(local)");
rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[0].colid = DB_NULLID;
// Database.
rgProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;
rgProperties[1].vValue.vt = VT_BSTR;
rgProperties[1].vValue.bstrVal = SysAllocString(L"AdventureWorks");
rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[1].colid = DB_NULLID;
rgProperties[2].dwPropertyID = DBPROP_AUTH_INTEGRATED;
rgProperties[2].vValue.vt = VT_BSTR;
rgProperties[2].vValue.bstrVal = SysAllocString(L"SSPI");
rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProperties[2].colid = DB_NULLID;
// Properties are now set. Next, construct DBPROPSET structure (rgInitPropSet) used to pass an
// array of DBPROP structures (InitProperties) to the SetProperties method.
rgPropSets[0].guidPropertySet = DBPROPSET_DBINIT;
rgPropSets[0].cProperties = cProperties;
rgPropSets[0].rgProperties = rgProperties;
// Get the IDBInitialize interface.
hr = CoCreateInstance(CLSID_MSOLEDBSQL,
NULL,
CLSCTX_INPROC_SERVER,
IID_IDBInitialize,
(void**)&pIDBInitialize);
if (FAILED(hr)) {
printf("Failed to get IDBInitialize interface.\n");
// Release any references and return.
goto Exit;
}
// Set initialization properties.
hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);
if (FAILED(hr)) {
printf("Failed to get IDBProperties interface.\n");
// Release any references and return.
goto Exit;
}
hr = pIDBProperties->SetProperties(cPropSets, rgPropSets);
if (FAILED(hr)) {
printf("Failed to set properties for DBPROPSET_DBINIT.\n");
// Release any references and return.
goto Exit;
}
hr = pIDBInitialize->Initialize();
if (FAILED(hr)) {
printf("Failed to initialize.\n");
// Release any references and return.
goto Exit;
}
// Create a session object.
hr = pIDBInitialize->QueryInterface( IID_IDBCreateSession,
(void **)&pIDBCreateSession);
if (FAILED(hr)) {
printf("Failed to get pIDBCreateSession interface.\n");
// Release any references and return.
goto Exit;
}
hr = pIDBCreateSession->CreateSession( NULL, IID_IDBCreateCommand, (IUnknown**)&pIDBCreateCommand);
if (FAILED(hr)) {
printf("Failed to create session object.\n");
// Release any references and return.
goto Exit;
}
// Get CommandText object
hr = pIDBCreateCommand->CreateCommand( NULL, riid, (IUnknown**)ppIUnknown);
if (FAILED(hr)) {
printf("Failed to create CommandText object.\n");
// Release any references and return.
goto Exit;
}
return hr;
Exit:
// Free up all allocated memory and release interface pointers.
return hr;
}
HRESULT CreateTable(ICommandText* pICommandText) {
HRESULT hr = S_OK;
// drop the table "TestISeqStream" if the table exists.
hr = pICommandText->SetCommandText( DBGUID_DBSQL, L"if object_id('TestISeqStream') is not null drop table TestISeqStream");
if (FAILED(hr)) {
printf("Failed to set command text DROP TABLE.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if (FAILED(hr)) {
printf("Failed to drop the table.\n");
// Release any references and return.
goto Exit;
}
// Create a new table.
hr = pICommandText->SetCommandText(DBGUID_DBSQL,
L"CREATE TABLE TestISeqStream (col1 int,col2 image)");
if (FAILED(hr)) {
printf("Failed to set command text CREATE TABLE.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if (FAILED(hr)) {
printf("Failed to create table.\n");
// Release any references and return.
goto Exit;
}
// Insert one row into table.
hr = pICommandText->SetCommandText(DBGUID_DBSQL,
L"INSERT INTO TestISeqStream(col1,col2) VALUES (1,0xAAAAAAAAAAAAAAAAA)");
if (FAILED(hr)) {
printf("Failed to set command text INSERT INTO.\n");
// Release any references and return.
goto Exit;
}
hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
if (FAILED(hr)) {
printf("Failed to insert record in the table.\n");
// Release any references and return.
goto Exit;
}
Exit:
// Release all allocated memory and release interface pointers.
return hr;
}