使用书签检索行 (OLE DB)
适用于：
SQL Server Azure SQL 数据库 Azure SQL 托管实例 Azure Synapse Analytics Analytics Platform System (PDW)
使用者可将绑定结构的 dwFlag 字段值设置为 DBCOLUMNSINFO_ISBOOKMARK，以指示将该列用作书签 。 使用者还可将行集属性 DBPROP_BOOKMARKS 设置为 VARIANT_TRUE。 这允许在行集中出现第 0 列。 然后，使用 IRowsetLocate::GetRowsAt 提取行（起始行的位置为书签加上一个偏移量得到的位置） 。
重要
请尽可能使用 Windows 身份验证。 如果 Windows 身份验证不可用，请在运行时提示用户输入其凭据。 不要将凭据存储在一个文件中。 如果必须保存凭据，应当用 Win32 crypto API（Win32 加密 API）加密它们。
使用书签检索行
建立与数据源的连接。
将行集 DBPROP_IRowsetLocate 属性设置为 VARIANT_TRUE。
执行命令。
对于将用作书签的列，请将绑定结构的 dwFlag 字段设置为 DBCOLUMNSINFO_ISBOOKMARK 标记 。
使用 IRowsetLocate::GetRowsAt 提取行（起始行为书签偏移量指定的行）。
示例
此示例显示如何使用书签提取行。 IA64 平台不支持此示例。
在该示例中，将从执行 SELECT 语句产生的结果集中检索第五行。
本文中的 Transact-SQL 代码示例使用 AdventureWorks2022 或 AdventureWorksDW2022 示例数据库，可从 Microsoft SQL Server 示例和社区项目主页下载它。
使用 ole32.lib 和 oleaut32.lib 编译并执行以下 C++ 代码列表。 此应用程序连接到您的计算机上默认的 SQL Server 实例。 在某些 Windows 操作系统上，您需要将 (localhost) 或 (local) 更改为您的 SQL Server 实例的名称。 若要连接到命名实例，请将连接字符串从 L"(local)" 更改为 L"(local)\\name"，其中 name 是命名实例。 默认情况下，SQL Server Express 安装在命名实例中。 请确保 INCLUDE 环境变量包括含有 msoledbsql.h 的目录。
// compile with: ole32.lib oleaut32.lib
int InitializeAndEstablishConnection();
int ProcessResultSet();
#define UNICODE
#define _UNICODE
#define DBINITCONSTANTS
#define INITGUID
#define OLEDBVER 0x0250 // to include correct interfaces
#include <stdio.h>
#include <tchar.h>
#include <stddef.h>
#include <windows.h>
#include <iostream>
#include <oledb.h>
#include <msoledbsql.h>
using namespace std;
IDBInitialize* pIDBInitialize = NULL;
IDBProperties* pIDBProperties = NULL;
IDBCreateSession* pIDBCreateSession = NULL;
IDBCreateCommand* pIDBCreateCommand = NULL;
ICommandProperties* pICommandProperties = NULL;
ICommandText* pICommandText = NULL;
IRowset* pIRowset = NULL;
IColumnsInfo* pIColumnsInfo = NULL;
DBCOLUMNINFO* pDBColumnInfo = NULL;
IAccessor* pIAccessor = NULL;
IRowsetLocate* pIRowsetLocate = NULL;
DBPROP InitProperties[4];
DBPROPSET rgInitPropSet[1];
DBPROPSET rgPropSets[1];
DBPROP rgProperties[1];
ULONG i, j;
HRESULT hresult;
DBROWCOUNT cNumRows = 0;
DBORDINAL lNumCols;
WCHAR* pStringsBuffer;
DBBINDING* pBindings;
DBLENGTH ConsumerBufferColOffset = 0;
HACCESSOR hAccessor;
DBCOUNTITEM lNumRowsRetrieved;
HROW hRows[5];
HROW* pRows = &hRows[0];
char* pBuffer;
int main() {
// The command to execute.
// WCHAR* wCmdString = OLESTR(" SELECT title_id, title FROM titles ");
WCHAR* wCmdString = OLESTR(" SELECT Name FROM Production.Product");
// Initialize and establish a connection to the data source.
if (InitializeAndEstablishConnection() == -1) {
// Handle error.
cout << "Failed to initialize and connect to the server.\n";
return -1;
}
// Create a session object.
if (FAILED(pIDBInitialize->QueryInterface(IID_IDBCreateSession, (void**) &pIDBCreateSession))) {
cout << "Failed to obtain IDBCreateSession interface.\n";
// Handle error.
return -1;
}
if (FAILED(pIDBCreateSession->CreateSession(NULL, IID_IDBCreateCommand, (IUnknown**) &pIDBCreateCommand))) {
cout << "pIDBCreateSession->CreateSession failed.\n";
// Handle error.
return -1;
}
// Access the ICommandText interface.
if (FAILED(pIDBCreateCommand->CreateCommand( NULL, IID_ICommandText, (IUnknown**) &pICommandText))) {
cout << "Failed to access ICommand interface.\n";
// Handle error.
return -1;
}
// Set DBPROP_IRowsetLocate
if (FAILED(pICommandText->QueryInterface( IID_ICommandProperties, (void **) &pICommandProperties ))) {
cout << "Failed to obtain ICommandProperties interface.\n";
// Handle error.
return -1;
}
// Set DBPROP_IRowsetLocate to VARIANT_TRUE to get the IRowsetLocate interface.
VariantInit(&rgProperties[0].vValue);
rgPropSets[0].guidPropertySet = DBPROPSET_ROWSET;
rgPropSets[0].cProperties = 1;
rgPropSets[0].rgProperties = rgProperties;
// Set properties in the property group (DBPROPSET_ROWSET)
rgPropSets[0].rgProperties[0].dwPropertyID = DBPROP_IRowsetLocate;
rgPropSets[0].rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
rgPropSets[0].rgProperties[0].colid = DB_NULLID;
rgPropSets[0].rgProperties[0].vValue.vt = VT_BOOL;
rgPropSets[0].rgProperties[0].vValue.boolVal= VARIANT_TRUE;
// Set the rowset properties.
hresult = pICommandText->QueryInterface( IID_ICommandProperties,(void **)&pICommandProperties);
if (FAILED(hresult)) {
printf("Failed to get ICommandProperties to set rowset properties.\n");
// Release any references and return.
return -1;
}
hresult = pICommandProperties->SetProperties(1, rgPropSets);
if (FAILED(hresult)) {
printf("Execute failed to set rowset properties.\n");
// Release any references and return.
return -1;
}
pICommandProperties->Release();
// Specify the command text.
if (FAILED(pICommandText->SetCommandText(DBGUID_DBSQL, wCmdString))) {
cout << "Failed to set command text.\n";
// Handle error.
return -1;
}
// Execute the command.
if (FAILED(hresult =
pICommandText->Execute( NULL, IID_IRowset, NULL, &cNumRows, (IUnknown **) &pIRowset))) {
cout << "Failed to execute command.\n";
// Handle error.
return -1;
}
ProcessResultSet();
pIRowset->Release();
// Free up memory.
pICommandText->Release();
pIDBCreateCommand->Release();
pIDBCreateSession->Release();
pIDBInitialize->Uninitialize();
pIDBInitialize->Release();
// Release COM library.
CoUninitialize();
return -1;
}
int InitializeAndEstablishConnection() {
// Initialize the COM library.
CoInitialize(NULL);
// Obtain access to the OLE DB Driver for SQL Server.
CoCreateInstance( CLSID_MSOLEDBSQL, NULL, CLSCTX_INPROC_SERVER, IID_IDBInitialize, (void **) &pIDBInitialize);
// Initialize the property values that are the same for each property.
for ( i = 0 ; i < 4 ; i++ ) {
VariantInit(&InitProperties[i].vValue);
InitProperties[i].dwOptions = DBPROPOPTIONS_REQUIRED;
InitProperties[i].colid = DB_NULLID;
}
// Server name.
InitProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
InitProperties[0].vValue.vt = VT_BSTR;
InitProperties[0].vValue.bstrVal = SysAllocString(L"(local)");
// Database.
InitProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;
InitProperties[1].vValue.vt = VT_BSTR;
InitProperties[1].vValue.bstrVal = SysAllocString(L"AdventureWorks");
InitProperties[2].dwPropertyID = DBPROP_AUTH_INTEGRATED;
InitProperties[2].vValue.vt = VT_BSTR;
InitProperties[2].vValue.bstrVal = SysAllocString(L"SSPI");
// Construct the PropertySet array.
rgInitPropSet[0].guidPropertySet = DBPROPSET_DBINIT;
rgInitPropSet[0].cProperties = 4;
rgInitPropSet[0].rgProperties = InitProperties;
// Set initialization properties.
pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);
hresult = pIDBProperties->SetProperties(1, rgInitPropSet);
if (FAILED(hresult)) {
cout << "Failed to set initialization properties.\n";
// Handle error.
return -1;
}
pIDBProperties->Release();
// Call the initialization method to establish the connection.
if (FAILED(pIDBInitialize->Initialize())) {
cout << "Problem initializing and connecting to the data source.\n";
// Handle error.
return -1;
}
return 0;
}
#ifdef _WIN64
#define BUFFER_ALIGNMENT 8
#else
#define BUFFER_ALIGNMENT 4
#endif
#define ROUND_UP(value) (value + (BUFFER_ALIGNMENT - 1) & ~(BUFFER_ALIGNMENT - 1))
int ProcessResultSet() {
HRESULT hr;
// Retrieve 5th row from the rowset (for example).
DBBKMARK iBookmark = 5;
pIRowset->QueryInterface(IID_IColumnsInfo, (void **)&pIColumnsInfo);
pIColumnsInfo->GetColumnInfo( &lNumCols, &pDBColumnInfo, &pStringsBuffer );
// Create a DBBINDING array.
pBindings = new DBBINDING[lNumCols];
if (!(pBindings /* = new DBBINDING[lNumCols] */ )) {
// Handle error.
return -1;
}
// Using the ColumnInfo strucuture, fill out the pBindings array.
for ( j = 0 ; j < lNumCols ; j++ ) {
pBindings[j].iOrdinal = j;
pBindings[j].obValue = ConsumerBufferColOffset;
pBindings[j].pTypeInfo = NULL;
pBindings[j].pObject = NULL;
pBindings[j].pBindExt = NULL;
pBindings[j].dwPart = DBPART_VALUE;
pBindings[j].dwMemOwner = DBMEMOWNER_CLIENTOWNED;
pBindings[j].eParamIO = DBPARAMIO_NOTPARAM;
pBindings[j].cbMaxLen = pDBColumnInfo[j].ulColumnSize + 1; // + 1 for null terminator
pBindings[j].dwFlags = 0;
pBindings[j].wType = pDBColumnInfo[j].wType;
pBindings[j].bPrecision = pDBColumnInfo[j].bPrecision;
pBindings[j].bScale = pDBColumnInfo[j].bScale;
// Recalculate the next buffer offset.
ConsumerBufferColOffset = ConsumerBufferColOffset + pDBColumnInfo[j].ulColumnSize;
ConsumerBufferColOffset = ROUND_UP(ConsumerBufferColOffset);
};
// Indicate that the first field is used as a bookmark by setting
// dwFlags to DBCOLUMNFLAGS_ISBOOKMARK.
pBindings[0].dwFlags = DBCOLUMNFLAGS_ISBOOKMARK;
// Get IAccessor interface.
hr = pIRowset->QueryInterface( IID_IAccessor, (void **)&pIAccessor);
if (FAILED(hr)) {
printf("Failed to get IAccessor interface.\n");
// Handle error.
return -1;
}
// Create accessor.
hr = pIAccessor->CreateAccessor( DBACCESSOR_ROWDATA,
lNumCols,
pBindings,
0,
&hAccessor,
NULL);
if (FAILED(hr)) {
printf("Failed to create an accessor.\n");
// Handle error.
return -1;
}
hr = pIRowset->QueryInterface( IID_IRowsetLocate, (void **) &pIRowsetLocate);
if (FAILED(hr)) {
printf("Failed to get IRowsetLocate interface.\n");
// Handle error.
return -1;
}
hr = pIRowsetLocate->GetRowsAt( 0,
NULL,
sizeof(DBBKMARK),
(BYTE *) &iBookmark,
0,
1,
&lNumRowsRetrieved,
&pRows);
if (FAILED(hr)) {
printf("Calling the GetRowsAt method failed.\n");
// Handle error.
return -1;
}
// Create buffer and retrieve data.
pBuffer = new char[ConsumerBufferColOffset];
if (!(pBuffer /* = new char[ConsumerBufferColOffset] */ )) {
// Handle error.
return -1;
}
memset(pBuffer, 0, ConsumerBufferColOffset);
hr = pIRowset->GetData(hRows[0], hAccessor, pBuffer);
if (FAILED(hr)) {
printf("Failed GetDataCall.\n");
// Handle error.
return -1;
}
char szTitle[7] = {0};
strncpy_s(szTitle, &pBuffer[pBindings[1].obValue], 6);
printf("%S\n", &pBuffer[pBindings[1].obValue]);
pIRowset->ReleaseRows(lNumRowsRetrieved, hRows, NULL, NULL, NULL);
// Release allocated memory.
delete [] pBuffer;
pIAccessor->ReleaseAccessor(hAccessor, NULL);
pIAccessor->Release();
delete [] pBindings;
return 0;
}