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Records and Streams

ADO currently provides the Recordset object as the primary means of accessing information in data sources, such as relational databases. However, some providers support the Record and Stream objects as alternative or complementary objects with which data from providers can be manipulated. For specifics on Record behavior, see your provider's documentation.

Record objects essentially function as one-row Recordsets. However, Records have limited functionality compared to Recordsets and they have different properties and methods.The source for the data in a Record object can be a command which returns one row of data from the provider. Using Record objects rather than Recordset objects to receive the results from a query that returns one row of data eliminates the overhead of instantiating the more complex Recordset object.

Record objects can serve another purpose, particularly with providers for data sources other than traditional relational databases, such as the Microsoft OLE DB Provider for Internet Publishing. Much of the information that must be processed exists, not as tables in databases, but as messages in electronic mail systems and files in modern file systems. The Record and Stream objects facilitate access to information stored in sources other than relational databases.

The Record object can represent and manage data such as directories and files in a file system or folders and messages in an e-mail system. For these purposes, the source for the Record can be the current row of an open Recordset, an absolute URL, or a relative URL in conjunction with an open Connection object.

Typically, a Recordset can be used to represent a container or parent in a hierarchy such as a folder or directory. A Record can be used to return specific information about one node in the parent container, such as a file or document. The primary reason Records are used to represent this type of information is that these sources of data are heterogeneous. This means that each Record may have a different set and number of fields. Traditional Recordsets containing rows from a database are homogenous, which means that each row has the same number and type of fields.

For more information about using the Record object for processing this heterogeneous data from providers such as the Internet Publishing Provider, see Using ADO for Internet Publishing.

The Stream object provides the means to read, write, and manage a stream of bytes. This byte stream may be text or binary and is limited in size only by system resources. Typically, ADO Stream objects are used for the following purposes:

  • To contain the data of a Recordset saved in XML format. These XML streams from saved Recordsets can be used as the source when opening a new Recordset. For more information, see Streams and Persistence.

  • To contain CommandStreams to be executed against the provider as an alternative to CommandText. For example, XML UpdateGrams can be used as the source for a command against the Microsoft OLE DB Provider for SQL Server.

  • To receive results from the provider in a format other than a Recordset, such as XML results from the Microsoft OLE DB Provider for SQL Server. For more information, see Retrieving Resultsets into Streams.

  • To contain the text or bytes that comprise a file or message, typically used with providers such as the Microsoft OLE DB Provider for Internet Publishing. For more information about this use of Stream objects, see Using ADO for Internet Publishing.

A Stream object can be opened on:

  • A simple file specified with a URL.

  • A field of a Record or Recordset containing a Stream object.

  • The default stream of a Record or Recordset object representing a directory or compound file.

  • A resource field containing the URL of a simple file.

  • No particular source at all. In this case, a Stream object is opened in memory. Data can be written to it and then saved in another Stream or file.

  • A BLOB field in a Recordset.

This section contains the following topics.

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