Visual Basic

Objects

[Recordset]

 

Recordset Object (ADO)

* Use Recordset (ADO/WFC Syntax) for search

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A Recordset object represents the entire set of records from a base table or the results of an executed command. At any time, the Recordset object refers to only a single record within the set as the current record.

Remarks

You use Recordset objects to manipulate data from a provider. When you use ADO, you manipulate data almost entirely using Recordset objects. All Recordset objects are constructed using records (rows) and fields (columns). Depending on the functionality supported by the provider, some Recordset methods or properties may not be available.

ADOR.Recordset and ADODB.Recordset are ProgIDs that you can use to create a Recordset object. The Recordset objects that result behave identically, regardless of the ProgID. The ADOR.Recordset is installed with Microsoft® Internet Explorer; the ADODB.Recordset is installed with ADO. The behavior of a Recordset object is affected by its environment (that is, client, server, Internet Explorer, and so on). Differences are noted in the Help topics for properties, methods, and events.

There are four different cursor types defined in ADO:

  • Dynamic cursor—allows you to view additions, changes, and deletions by other users, and allows all types of movement through the Recordset that don't rely on bookmarks; allows bookmarks if the provider supports them.

  • Keyset cursor—behaves like a dynamic cursor, except that it prevents you from seeing records that other users add, and prevents access to records that other users delete. Data changes by other users will still be visible. It always supports bookmarks and therefore allows all types of movement through the Recordset.

  • Static cursor—provides a static copy of a set of records for you to use to find data or generate reports; always allows bookmarks and therefore allows all types of movement through the Recordset. Additions, changes, or deletions by other users will not be visible. This is the only type of cursor allowed when you open a client-side (ADOR) Recordset object.

  • Forward-only cursor—behaves identically to a dynamic cursor except that it allows you to scroll only forward through records. This improves performance in situations where you need to make only a single pass through a Recordset.

Set the CursorType property prior to opening the Recordset to choose the cursor type, or pass a CursorType argument with the Open method. Some providers don’t support all cursor types. Check the documentation for the provider. If you don't specify a cursor type, ADO opens a forward-only cursor by default.

When used with some providers (such as the Microsoft ODBC Provider for OLE DB in conjunction with Microsoft SQL Server), you can create Recordset objects independently of a previously defined Connection object by passing a connection string with the Open method. ADO still creates a Connection object, but it doesn't assign that object to an object variable. However, if you are opening multiple Recordset objects over the same connection, you should explicitly create and open a Connection object; this assigns the Connection object to an object variable. If you do not use this object variable when opening your Recordset objects, ADO creates a new Connection object for each new Recordset, even if you pass the same connection string.

You can create as many Recordset objects as needed.

When you open a Recordset, the current record is positioned to the first record (if any) and the BOF and EOF properties are set to False. If there are no records, the BOF and EOF property settings are True.

You can use the MoveFirst, MoveLast, MoveNext, and MovePrevious methods, as well as the Move method, and the AbsolutePosition, AbsolutePage, and Filter properties to reposition the current record, assuming the provider supports the relevant functionality. Forward-only Recordset objects support only the MoveNext method. When you use the Move methods to visit each record (or enumerate the Recordset), you can use the BOF and EOF properties to see if you've moved beyond the beginning or end of the Recordset.

Recordset objects can support two types of updating: immediate and batched. In immediate updating, all changes to data are written immediately to the underlying data source once you call the Update method. You can also pass arrays of values as parameters with the AddNew and Update methods and simultaneously update several fields in a record.

If a provider supports batch updating, you can have the provider cache changes to more than one record and then transmit them in a single call to the database with the UpdateBatch method. This applies to changes made with the AddNew, Update, and Delete methods. After you call the UpdateBatch method, you can use the Status property to check for any data conflicts in order to resolve them.

Note   To execute a query without using a Command object, pass a query string to the Open method of a Recordset object. However, a Command object is required when you want to persist the command text and re-execute it, or use query parameters.