OLE DB-Parameter (SQL Server Compact)

Microsoft SQL Server Compact 3.5 (SQL Server Compact 3.5) unterstützt Abfragen, die Parameter enthalten. Parameter können für das Ersetzen von Spaltenwerten in Abfragen verwendet werden.

Verwenden von Parametern

Sie können Informationen zu den Parametern eines Befehls, beispielsweise deren Datentypen, mithilfe von ICommandWithParameters::GetParameterInfo abrufen. Parameter werden dann übergeben, wenn ICommand::Execute aufgerufen wird.

Beispiele

Im folgenden Beispiel wird OLE DB verwendet, um eine neue Zeile in die Shippers-Tabelle einzufügen. Beachten Sie, dass Sie dieses Beispiel sowohl auf 32-Bit- als auch auf 64-Bit-Plattformen kompilieren und ausführen können. Weitere Informationen finden Sie im Informationsthema zu OLE DB 64-Bit in der Visual Studio 2008 SP1-Dokumentation.

// Start the method to insert data using parameters.
// Declarations
HRESULT                  hr;
IDBInitialize *          pIDBInitialize    = NULL;
IDBProperties *          pIDBProperties    = NULL;
IDBCreateSession *       pIDBCrtSession    = NULL;
DBPROPSET                rgPropSets[1];
DBPROP                   rgProps[1];
ULONG                    iPropSet          = 0;
ULONG                    iProp             = 0;
ICommandText *           pICmdText         = NULL;
IDBCreateCommand *       pIDBCrtCmd        = NULL;
ICommandPrepare *        pICmdPrepare      = NULL;
ICommandWithParameters * pICmdWParams      = NULL;
IAccessor *              pIAcc             = NULL;
DB_UPARAMS               cParams;
DBPARAMINFO *            rgParamInfo       = NULL;
OLECHAR *                pNamesBuffer      = NULL;
DBCOUNTITEM              cBindings;
DBBINDING                rgBindings[3];
DBBYTEOFFSET             cbRowSize;
HACCESSOR                hAcc;
BYTE *                   pData             = NULL;
DBPARAMS                 params;
DBROWCOUNT               cRowsAffected;

// Specify the MyDB database as wzDbName.
WCHAR  wzDbName[]  = L"\\windows\\MyDB.sdf";
ULONG i;

// Initialize the property set values.and create the data source object.

for (i = 0; i < sizeof(rgProps)/sizeof(rgProps[0]); i++)
{
VariantInit(&rgProps[i].vValue);
}

hr = CoCreateInstance(CLSID_SQLSERVERCE, NULL, CLSCTX_INPROC_SERVER, 
IID_IDBInitialize, (LPVOID *) &pIDBInitialize);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

iProp = 0;
rgProps[iProp].dwPropertyID   = DBPROP_INIT_DATASOURCE;
rgProps[iProp].dwOptions = DBPROPOPTIONS_REQUIRED;
rgProps[iProp].vValue.vt = VT_BSTR;
rgProps[iProp].vValue.bstrVal = SysAllocString(wzDbName);
if(!(rgProps[iProp].vValue.bstrVal))
{
hr = E_OUTOFMEMORY;
goto Exit; 
}
iProp++;

iPropSet = 0;
rgPropSets[iPropSet].rgProperties    = rgProps;
rgPropSets[iPropSet].cProperties     = iProp;
rgPropSets[iPropSet].guidPropertySet = DBPROPSET_DBINIT;
iPropSet++;

// Set the properties into the provider's data source object.
pIDBInitialize->QueryInterface(IID_IDBProperties,(void**)&pIDBProperties);

hr = pIDBProperties->SetProperties(sizeof(rgPropSets)/sizeof(rgPropSets[iPropSet]), 
rgPropSets);
if(FAILED(hr))
{
goto Exit;
}

// Create a session that supports commands.
hr = pIDBProperties->QueryInterface(IID_IDBCreateSession, (void **) 
&pIDBCrtSession);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

hr = pIDBCrtSession->CreateSession(NULL, IID_IDBCreateCommand,
(IUnknown**) &pIDBCrtCmd);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}


// Create the new command that uses parameters.
hr = pIDBCrtCmd->CreateCommand(NULL, IID_ICommandWithParameters,
(IUnknown**) &pICmdWParams);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

hr = pICmdWParams->QueryInterface(IID_ICommandText, (void**) &pICmdText);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

hr = pICmdWParams->QueryInterface(IID_ICommandPrepare, (void**) &pICmdPrepare);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

// Specify the command text using parameter markers in the query syntax.
hr = pICmdText->SetCommandText(DBGUID_DBSQL, L"INSERT INTO Shippers \
(ShipperID, CompanyName, Phone) VALUES (?, ?, ?)");
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

// Prepare the current command.
hr = pICmdPrepare->Prepare(1);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

// Retrieving parameter information
hr = pICmdWParams->GetParameterInfo(&cParams, &rgParamInfo, &pNamesBuffer);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

// Create the acessor object and column specific bindings.

hr = pICmdText->QueryInterface(IID_IAccessor, (void**) &pIAcc);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

// Create the bindings for the three columns.
cBindings = 3;

rgBindings[0].iOrdinal = 1;
rgBindings[0].obStatus = 0;
rgBindings[0].obLength = rgBindings[0].obStatus + sizeof(DBSTATUS);
rgBindings[0].obValue = rgBindings[0].obLength + sizeof(DBLENGTH);
rgBindings[0].pTypeInfo = NULL;
rgBindings[0].pObject = NULL;
rgBindings[0].pBindExt = NULL;
rgBindings[0].dwPart = DBPART_VALUE | DBPART_LENGTH | DBPART_STATUS;
rgBindings[0].dwMemOwner = DBMEMOWNER_CLIENTOWNED;
rgBindings[0].eParamIO = DBPARAMIO_INPUT;
rgBindings[0].cbMaxLen = sizeof(int); //ShipperID is integer
rgBindings[0].dwFlags = 0;
rgBindings[0].wType = DBTYPE_I4;
rgBindings[0].bPrecision = 0;
rgBindings[0].bScale = 0;

rgBindings[1].iOrdinal = 2;
rgBindings[1].obStatus = rgBindings[0].obValue + rgBindings[0].cbMaxLen;
rgBindings[1].obLength = rgBindings[1].obStatus + sizeof(DBSTATUS);
rgBindings[1].obValue = rgBindings[1].obLength + sizeof(DBLENGTH);
rgBindings[1].pTypeInfo = NULL;
rgBindings[1].pObject = NULL;
rgBindings[1].pBindExt = NULL;
rgBindings[1].dwPart = DBPART_VALUE | DBPART_LENGTH | DBPART_STATUS;
rgBindings[1].dwMemOwner = DBMEMOWNER_CLIENTOWNED;
rgBindings[1].eParamIO = DBPARAMIO_INPUT;
rgBindings[1].cbMaxLen = 40 * sizeof(WCHAR); //CompanyName is nvarchar(40)
rgBindings[1].dwFlags = 0;
rgBindings[1].wType = DBTYPE_WSTR;
rgBindings[1].bPrecision = 0;
rgBindings[1].bScale = 0;

rgBindings[2].iOrdinal = 3;
rgBindings[2].obStatus = rgBindings[1].obValue + rgBindings[1].cbMaxLen;
rgBindings[2].obLength = rgBindings[2].obStatus + sizeof(DBSTATUS);
rgBindings[2].obValue = rgBindings[2].obLength + sizeof(DBLENGTH);
rgBindings[2].pTypeInfo = NULL;
rgBindings[2].pObject = NULL;
rgBindings[2].pBindExt = NULL;
rgBindings[2].dwPart = DBPART_VALUE | DBPART_LENGTH | DBPART_STATUS;
rgBindings[2].dwMemOwner = DBMEMOWNER_CLIENTOWNED;
rgBindings[2].eParamIO = DBPARAMIO_INPUT;
rgBindings[2].cbMaxLen = 24 * sizeof(WCHAR); //Phone is nvarchar(24)
rgBindings[2].dwFlags = 0;
rgBindings[2].wType = DBTYPE_WSTR;
rgBindings[2].bPrecision = 0;
rgBindings[2].bScale = 0;

// Calculate the total memory needed for the input buffer.
cbRowSize = rgBindings[2].obValue + rgBindings[2].cbMaxLen;


// Create the accessor for the parameter data. 
hr = pIAcc->CreateAccessor(DBACCESSOR_PARAMETERDATA, cBindings,
rgBindings, cbRowSize, &hAcc, NULL);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}

// Allocate memory for the parameter data.
pData = (BYTE*) malloc(cbRowSize);
if(!(pData))
{
hr = E_OUTOFMEMORY;
goto Exit; 
}

//Clear out the buffer.
memset(pData, 0, cbRowSize);
 
// Define the insert data for the parameters.
// Shipper ID
* (DBSTATUS*) (pData + rgBindings[0].obStatus) = DBSTATUS_S_OK;
* (int*)   (pData + rgBindings[0].obValue)  = 1;
* (DBLENGTH*)   (pData + rgBindings[0].obLength) = sizeof(int);

// CompanyName
* (DBSTATUS*) (pData + rgBindings[1].obStatus) = DBSTATUS_S_OK;
wcscpy((WCHAR*) (pData + rgBindings[1].obValue), L"Federal Express");
* (DBLENGTH*)   (pData + rgBindings[1].obLength)  = wcslen(L"Federal Express") * sizeof(WCHAR);

// Phone
* (DBSTATUS*) (pData + rgBindings[2].obStatus) = DBSTATUS_S_OK;
wcscpy((WCHAR*) (pData + rgBindings[2].obValue), L"1-800-555-1212");
* (DBLENGTH*)   (pData + rgBindings[2].obLength)  = wcslen(L"1-800-555-1212") * sizeof(WCHAR);

// Define the DBPARAMS structure.
params.pData = pData;
params.cParamSets = 1;
params.hAccessor = hAcc;

// Execute the command with paramters.
hr = pICmdText->Execute(NULL, IID_NULL, &params, &cRowsAffected, NULL);

// Error handling for the command
if (FAILED(hr) || (1 != cRowsAffected))
{
MessageBox(NULL,L"An error occurred",L"error",MB_OK);
}

Exit:

// Clean up resources.

free(pData);
CoTaskMemFree(rgParamInfo);
CoTaskMemFree(pNamesBuffer);

if(pIAcc)   pIAcc->Release();
if(pIDBProperties) pIDBProperties->Release();
if(pIDBCrtSession) pIDBCrtSession->Release();
if(pICmdPrepare) pICmdPrepare->Release();
if(pICmdWParams) pICmdWParams->Release();
if(pICmdText)  pICmdText->Release();
if(pIDBCrtCmd)  pIDBCrtCmd->Release();

for(i = 0; i < sizeof(rgProps)/sizeof(rgProps[0]); i++)
{
VariantClear(&rgProps[i].vValue);
}

return;