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.

For more information on	Go to
Rowset objects	Rowsets
Row objects	Row Objects (OLE DB)
Creating row objects	Creating Row Objects
Row status	DBROWSTASTUS Enumerated Type (OLE DB)
Row metadata	Row Metadata
Special row column DBIDs	Special Row Column DBIDs
Column values	Column Values
Transactions on row objects	Transactions on Row Objects
How to support row objects	Provider and Consumer Support for Row Objects
Stream objects	Stream Objects (OLE DB)
Modeling tree-structured namespaces	Modeling Tree-Structured Namespaces
Direct binding in tree-structured namespaces	Direct Binding in Tree-Structured Namespaces
Navigating tree-structured namespaces	Navigating Tree-Structured Namespaces
Scoped tree manipulation operations	Scoped Tree Manipulation Operations
Resource rowsets and document source providers	Resource Rowsets and Document Source Providers
Direct binding	Binder Objects and Direct Binding

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.

Interface	Use
IColumnsInfo	Provides information about the columns of the row object.
IConvertType	Provides information about the data type conversions supported by the row object.
IGetSession	Returns an interface pointer on the session object within whose context the row object was created.
IRow	Contains methods for reading column data from a row object and for obtaining the source rowset of the row object, if one exists.

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)