MoveFirst, MoveLast, MoveNext, and MovePrevious Methods

Applies To

OraDynaset Object

Description

Change the cursor position to the first, last, next, or previous row within the specified dynaset. These move methods move the cursor to the next (previous, and so on) valid row, skipping rows that have been deleted.

Usage

oradynaset.MoveFirst
oradynaset.DbMoveFirst

oradynaset.MoveLast
oradynaset.DbMoveLast  

oradynaset.MovePrevious
oradynaset.DbMovePrevious  

oradynaset.MoveNext
oradynaset.DbMoveNext  

Remarks

The data control buttons map (from left to right or from top to bottom) to the MoveFirst, MovePrevious, MoveNext, and MoveLast methods. The BOF and EOF properties are never true when using the data control buttons.

When the first or last record is current, record movement does not occur if you use the MoveFirst or MoveLast methods, respectively. You force the query to completion if you use the MoveLast method on a dynaset.

If you use the MovePrevious method and the first record is current, there is no current record and BOF is true. Using the MovePrevious method again causes an error, although BOF remains True. If you use the MoveNext method and the last record is current, there is no current record and EOF is true. Using the MoveNext method again causes an error, although EOF remains true. Note that when the dynaset is created with the ORADYN_NO_MOVEFIRST option, BOF and EOF are true whether the dynaset is empty or not.

When you open a dynaset, BOF is False and the first record is current. If a dynaset is empty, BOF and EOF are both true, and there is no current record.

If an Edit or AddNew operation is pending and you use one of the Move methods indirectly by way of the data control, then the Update method is invoked automatically, although, it can be stopped during the Validate event.

If an Edit or AddNew operation is pending and you use one of the Move methods directly without the data control, pending Edit or AddNew operations cause existing changes to be lost, although no error occurs.

Data is fetched from the database, as necessary, so performing a MoveFirst operation followed by a MoveNext operation incrementally builds the mirrored (cached) local set without requiring read-ahead of additional data. However, executing a MoveLast operation requires that the entire query be evaluated and stored locally.

When a dynaset is attached to a data control, these methods first notify the Validate event of the data control that record motion is about to occur. The Validate handler can deny the request for motion, in which case the request is ignored. If the record pointer is successfully moved, then all custom controls attached to the data control are notified automatically of the new record position.

Examples

This example demonstrates record movement within a dynaset using the MoveFirst, MoveNext, MoveLast, MovePrevious methods. Copy and paste this code into the definition section of a form. Then, press F5.

Sub Form_Load ()
 
 'Declare variables 
 Dim OraSession As OraSession 
 Dim OraDatabase As OraDatabase 
 Dim OraDynaset As OraDynaset 
 
 'Create the OraSession Object.
 Set OraSession = CreateObject("OracleInProcServer.XOraSession")
 
 'Create the OraDatabase Object by opening a connection to Oracle.
 Set OraDatabase = OraSession.OpenDatabase("ExampleDb", "scott/tiger", 0&)
 
 'Create the OraDynaset Object.
 Set OraDynaset = OraDatabase.CreateDynaset("select empno, ename from emp", 0&)
 
MsgBox "Employee #" & OraDynaset.Fields("empno").value & ", " & _
             OraDynaset.Fields("ename").value
 
 'Move to the next record and display it.
 OraDynaset.MoveNext
 MsgBox "Employee #" & OraDynaset.Fields("empno").value & ", " & _
              OraDynaset.Fields("ename").value
 
 'Move to the last record and display it.
 OraDynaset.MoveLast
 MsgBox "Employee #" & OraDynaset.Fields("empno").value & ", " & _
              OraDynaset.Fields("ename").value
 
 'Move to the previous record and display it.
 OraDynaset.MovePrevious
 MsgBox "Employee #" & OraDynaset.Fields("empno").value & ", " & _
             OraDynaset.Fields("ename").value
 
 
End Sub