Field.AppendChunk method (DAO)

Applies to: Access 2013, Office 2013

Appends data from a string expression to a Memo or Long Binary Field object in a Recordset.

Syntax

expression .AppendChunk(Val)

expression A variable that represents a Field object.

Parameters

Name	Required/optional	Data type	Description
Val	Required	Variant	A Variant (String subtype) expression or variable containing the data you want to append to the Field object.

Remarks

You can use the AppendChunk and GetChunk methods to access subsets of data in a Memo or Long Binary field.

You can also use these methods to conserve string space when you work with Memo and Long Binary fields. Certain operations (copying, for example) involve temporary strings. If string space is limited, you may need to work with chunks of a field instead of the entire field.

If there is no current record when you use AppendChunk, an error occurs.

Note

The initial AppendChunk operation (after an Edit or AddNew call) will simply place the data in the field, overwriting any existing data. Subsequent AppendChunk calls within the same Edit or AddNew session will then add to the existing data.

Example

This example uses the AppendChunk and GetChunk methods to fill an OLE object field with data from another record, 32K at a time. In a real application, one might use a procedure like this to copy an employee record (including the employee's photo) from one table to another. In this example, the record is simply being copied back to same table. Note that all the chunk manipulation takes place within a single AddNew-Update sequence.

    Sub AppendChunkX() 
     
       Dim dbsNorthwind As Database 
       Dim rstEmployees As Recordset 
       Dim rstEmployees2 As Recordset 
     
       Set dbsNorthwind = OpenDatabase("Northwind.mdb") 
     
       ' Open two recordsets from the Employees table. 
       Set rstEmployees = _ 
          dbsNorthwind.OpenRecordset("Employees", _ 
          dbOpenDynaset) 
       Set rstEmployees2 = rstEmployees.Clone 
     
       ' Add a new record to the first Recordset and copy the  
       ' data from a record in the second Recordset. 
       With rstEmployees 
          .AddNew 
          !FirstName = rstEmployees2!FirstName 
          !LastName = rstEmployees2!LastName 
          CopyLargeField rstEmployees2!Photo, !Photo 
          .Update 
     
          ' Delete new record because this is a demonstration. 
          .Bookmark = .LastModified 
          .Delete 
          .Close 
       End With 
     
       rstEmployees2.Close 
       dbsNorthwind.Close 
     
    End Sub 
     
    Function CopyLargeField(fldSource As Field, _ 
       fldDestination As Field) 
     
       ' Set size of chunk in bytes. 
       Const conChunkSize = 32768 
     
       Dim lngOffset As Long 
       Dim lngTotalSize As Long 
       Dim strChunk As String 
     
       ' Copy the photo from one Recordset to the other in 32K  
       ' chunks until the entire field is copied. 
       lngTotalSize = fldSource.FieldSize 
       Do While lngOffset < lngTotalSize 
          strChunk = fldSource.GetChunk(lngOffset, conChunkSize) 
          fldDestination.AppendChunk strChunk 
          lngOffset = lngOffset + conChunkSize 
       Loop 
     
    End Function