Reads the data from the
RAW field into byte array and returns the size of data read.
The arguments for the method are:
||The first element of the
||The number of bytes in the field to skip before copying data.|
||The number of bytes to copy.|
When possible, the
GetChunkByte method retrieves the specified bytes from the local cache. However, to conserve resources, some of the data might not be stored locally. In these cases, the
GetChunkByte method requests the necessary data from the database as required. As part of this process, data from all fields (except the Long or
RAW field) in the dynaset are retrieved and compared with the cached values for consistency. If any changes have occurred since the fetch of the original partial data, then the
GetChunkByte method stops the operation and an error occurs. In the case of an abort, the returned string is
RAW field is less than 65280 bytes in size, it is quicker to retrieve the data using the
Value property than using the
GetChunkByte method. You cannot use the
GetChunkByte method on a
RAW field for which you have created an alias.
This example demonstrates the use of the
GetChunkByte method to retrieve a
RAW column of a database and save it as a file. This example expects a valid dynaset named
OraDynaset representing a table with a column named
longraw. Copy and paste this code into the definition section of a form. Call this procedure with a valid file name.
Sub GetChunkByteExample (FName As String) 'Declare various variables Dim CurSize As Integer, ChunkSize As Long Dim I As Integer, FNum As Integer, CurChunk() As Byte 'Set the size of each chunk ChunkSize = 10240 'Redim CurChunk Array ReDim CurChunk(ChunkSize) frmChunk.MousePointer = HOURGLASS 'Get a free file number FNum = FreeFile 'Open the file Open FName For Binary As #FNum I = 0 'Loop through all of the chunks 'Oracle does not return the size of columns > 64KB. We should loop until the 'length of our block is less than we asked for. Do CurSize = OraDynaset.Fields("type_longraw").GetChunkByte(CurChunk(0), I * ChunkSize, ChunkSize) If CurSize > 0 AND CurSize < ChunkSize Then ReDim CurChunk(CurSize) CurSize = OraDynaset.Fields("type_longraw").GetChunkByte(CurChunk(0), I * ChunkSize, CurSize) End If Put #FNum, , CurChunk 'Write chunk to file. I = I + 1 Loop Until CurSize <= 0 'Close the file. Close FNum frmChunk.MousePointer = DEFAULT End Sub
See Also:"Migration from LONG RAW to LOB or BFILE" for additional information