如何使用 OLE DB 指定临时数据库的位置（以编程方式）
本主题将介绍如何在使用 Visual C++ 编写 OLE DB 应用程序时设置临时数据库文件的位置和大小。您可以通过在数据源初始化或在 ISSCECompact::Compact 方法运行时指定 DBPROP_SSCE_TEMPFILE_DIRECTORY 属性来设置临时数据库的位置。数据库大小通过指定 DBPROP_SSCE_TEMPFILE_MAX_SIZE 属性进行设置。
示例
下面的示例说明在调用 IDBProperties::SetProperties 时如何通过指定 DBPROP_SSCE_TEMPFILE_DIRECTORY 属性来指定临时数据库目录：
// Object declarations
HRESULT hr = NOERROR;
DBPROPSET dbpropset[2];
DBPROP dbprop[1];
DBPROP sscedbprop[1];
// Declare the provider interfaces.
IDBInitialize * pIDBInitialize = NULL;
IDBProperties * pIDBProperties = NULL;
// Initialize the data source.
hr = CoCreateInstance(CLSID_SQLSERVERCE_3_0, 0, CLSCTX_INPROC_SERVER,
IID_IDBInitialize, (void**) &pIDBInitialize);
if (FAILED(hr))
{
//Send an error-specific message and do error handling.
goto Exit;
}
// Initialize property structures
VariantInit(&dbprop[0].vValue);
VariantInit(&sscedbprop[0].vValue);
// Initialize Property with name of database.
dbprop[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
dbprop[0].dwOptions = DBPROPOPTIONS_REQUIRED;
dbprop[0].vValue.vt = VT_BSTR;
dbprop[0].vValue.bstrVal = SysAllocString(L"MyDB.sdf");
if(NULL == dbprop[0].vValue.bstrVal)
{
hr = E_OUTOFMEMORY;
goto Exit;
}
// Second property set has one property that contains the provider-specific
// property to specify an alternative temp file directory.
sscedbprop[0].dwPropertyID = DBPROP_SSCE_TEMPFILE_DIRECTORY;
sscedbprop[0].vValue.vt = VT_BSTR;
sscedbprop[0].vValue.bstrVal = SysAllocString(L"\\NewTempDir");
if(NULL == dbprop[0].vValue.bstrVal)
{
hr = E_OUTOFMEMORY;
goto Exit;
}
// Initialize property set.
dbpropset[0].guidPropertySet = DBPROPSET_DBINIT;
dbpropset[0].rgProperties = dbprop;
dbpropset[0].cProperties = sizeof(dbprop)/sizeof(dbprop[0]);
// Initialize the provider-specific property set.
dbpropset[1].guidPropertySet = DBPROPSET_SSCE_DBINIT;
dbpropset[1].rgProperties = sscedbprop;
dbpropset[1].cProperties = sizeof(sscedbprop)/sizeof(sscedbprop[0]);
// Set the properties into the provider's data source object.
pIDBInitialize->QueryInterface(IID_IDBProperties,(void**)&pIDBProperties);
hr = pIDBProperties->SetProperties(sizeof(dbpropset)/sizeof(dbpropset[0]),
dbpropset);
if(FAILED(hr))
{
goto Exit;
}
// Initialize the data source.
hr = pIDBInitialize->Initialize();
if(FAILED(hr))
{
goto Exit;
}
Exit:
//Clean up resources here
return;