Row and Stream Objects (OLE DB)

OLE DB provides rowset objects for accessing information in data stores, such as relational databases, in which data is formatted into tables. However, not all structured data can easily be viewed as tables. This is especially true of heterogeneous hierarchical data such as directories and files in a file system or folders and messages in an e-mail system.

OLE DB 2.5 introduces the row object, which is an OLE DB object that contains a set of columns of data. A row object can represent a row in a rowset, the result of a singleton SQL SELECT statement, or a node in a tree-structured namespace, such as a file in a directory or a message in a mail folder.

OLE DB 2.5 also introduces the OLE DB stream object, which encapsulates the contents of files, e-mail messages, or other stream-based objects. A stream object is a specialized storage object that exposes the COM IStream interface. Stream objects are created from a row object and reference the parent object.

This section discusses the use of row and stream objects.

The row object cotype is defined as follows. For more information about cotypes, see Conceptual Programming Models in OLE DB.

CoType TRow {
   [mandatory]   interface IColumnsInfo;
   [mandatory]   interface IConvertType;
   [mandatory]   interface IGetSession;
   [mandatory]   interface IRow;
   [optional]    interface IColumnsInfo2;
   [optional]    interface IConnectionPointContainer;
   [optional]    interface ICreateRow;
   [optional]    interface IDBAsynchStatus;
   [optional]    interface IDBCreateCommand;
   [optional]    interface IDBInitialize;
   [optional]    interface IRowChange;
   [optional]    interface IRowSchemaChange;
   [optional]    interface IScopedOperations;
   [optional]    interface ISupportErrorInfo;
}

Remarks

All row objects must expose the interfaces listed in the following table.

This section contains the following topics:

• Row Objects (OLE DB)

• Stream Objects (OLE DB)

• Modeling Tree-Structured Namespaces

• Resource Rowsets and Document Source Providers

• DBROWSTATUS Enumerated Type (OLE DB)