---
title: "Accessing XML Data"
ms.date: "10/18/2018"
helpviewer_keywords: ["data access [C++], XML data", "XML [C++], accessing data", "CXMLAccessor class, retrieving XML data", "data [C++], XML data access", "rowsets [C++], retrieving XML data", "CStreamRowset class, retrieving XML data"]
ms.assetid: 6b693d55-a554-4846-8118-e8773b79b572
---
# Accessing XML Data

There are two separate methods of retrieving XML data from a data source: one uses [CStreamRowset](../../data/oledb/cstreamrowset-class.md) and the other uses [CXMLAccessor](../../data/oledb/cxmlaccessor-class.md).

|Functionality|CStreamRowset|CXMLAccessor|
|-------------------|-------------------|------------------|
|Amount of data transferred|Retrieves data from all columns and rows at once.|Retrieves data from all columns but only one row at a time. You must navigate rows using methods such as `MoveNext`.|
|Formatting the string|SQL Server formats the XML string and sends it to the consumer.|Retrieves rowset data in its native format (requests that the provider send it as Unicode strings) and then builds the string holding the data in XML format.|
|Control over formatting|You have some level of control over how the XML string is formatted by setting some SQL Server 2000-specific properties.|You have no control over the format of the generated XML string.|

While `CStreamRowset` provides a more overall efficient way of retrieving data in XML format, it's only supported by SQL Server 2000.

## Retrieving XML Data Using CStreamRowset

You specify [CStreamRowset](../../data/oledb/cstreamrowset-class.md) as the rowset type in your `CCommand` or `CTable` declaration. You can use it with your own accessor or no accessor, for example:

```cpp
CCommand<CAccessor<CMyAccessor>, CStreamRowset> myCmd;
```

-or-

```cpp
CCommand<CNoAccessor, CStreamRowset> myCmd;
```

Normally when you call `CCommand::Open` (specifying, for example, `CRowset` as the `TRowset` class), it gets an `IRowset` pointer. `ICommand::Execute` returns an `IRowset` pointer, which is stored in the `m_spRowset` member of the `CRowset` object. Methods such as `MoveFirst`, `MoveNext`, and `GetData` use that pointer to retrieve the data.

By contrast, when you call `CCommand::Open` (but specify `CStreamRowset` as the `TRowset` class), `ICommand::Execute` returns an `ISequentialStream` pointer, which is stored in the `m_spStream` data member of [CStreamRowset](../../data/oledb/cstreamrowset-class.md). You then use the `Read` method to retrieve the (Unicode string) data in XML format. For example:

```cpp
myCmd.m_spStream->Read()
```

SQL Server 2000 does the XML formatting and returns all columns and all rows of the rowset as one XML string.

For an example using the `Read` method, see **Adding XML Support to the Consumer** in [Implementing a Simple Consumer](../../data/oledb/implementing-a-simple-consumer.md).

> [!NOTE]
> XML support using `CStreamRowset` works with SQL Server 2000 only and requires that you have the OLE DB Provider for SQL Server 2000 (installed with MDAC).

## Retrieving XML Data Using CXMLAccessor

[CXMLAccessor](../../data/oledb/cxmlaccessor-class.md) allows you to access data from a data source as string data when you have no knowledge of the data store's schema. `CXMLAccessor` works like `CDynamicStringAccessorW` except that the former converts all data accessed from the data store as XML-formatted (tagged) data. The XML tag names match the data store's column names as closely as possible.

Use `CXMLAccessor` as you would any other accessor class, passing it as a template parameter to `CCommand` or `CTable`:

```cpp
CTable<CXMLAccessor, CRowset> rs;
```

Use [GetXMLRowData](../../data/oledb/cxmlaccessor-getxmlrowdata.md) to retrieve data from the table one row at a time, and navigate rows using methods such as `MoveNext`, for example:

```cpp
// Open data source, session, and rowset
hr = rs.MoveFirst();

while(SUCCEEDED(hr) && hr != DB_S_ENDOFROWSET )
{
    CStringW strRowData;
    myCmd.GetXMLRowData(strRowData);

    printf_s( "%S\n", strRowData );

    hr = rs.MoveNext();
}
```

You can use [GetXMLColumnData](../../data/oledb/cxmlaccessor-getxmlcolumndata.md) to retrieve the column (data type) information as XML-formatted string data.

## See also

[Using Accessors](../../data/oledb/using-accessors.md)