Microsoft KB Archive/197916

= How To Use GUIDs w/ Access, SQL 6.5 and SQL 7 =

Article ID: 197916

Article Last Modified on 8/5/2004

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APPLIES TO


 * Microsoft Visual Basic 5.0 Enterprise Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition
 * Microsoft Data Access Components 1.5
 * Microsoft Data Access Components 2.0
 * Microsoft Data Access Components 2.1 Service Pack 2
 * Microsoft Data Access Components 2.5
 * Microsoft Data Access Components 2.6

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This article was previously published under Q197916



SUMMARY
AdoGUIDz.exe is a self-extracting executable that contains a sample project that demonstrates using the globally unique identifier datatype (GUID) with Microsoft Access, SQL 6.5 and SQL 7.0. The sample code may be particularly helpful if you are attempting to manipulate GUIDs with ODBC versions 3.51 and below because those versions of ODBC do not support a native GUID datatype. ODBC versions 3.6 and above include the GUID datatype. Consequently, the methods for manipulating GUIDs with ODBC 3.6 are simpler.

NOTE: SQL 6.5 does not support a native GUID datatype so in order to store/retrieve GUIDs in SQL 6.5 you must use the VarBinary datatype and Byte Arrays.



MORE INFORMATION
The following files are available for download from the Microsoft Download Center:

Adoguidz.exe

Release Date: DEC-29-1998

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.   FileName                  Size -

AdoGUID.bas                3KB AdoGUID.exe               60KB AdoGUID.frm               25KB AdoGUID.frx                1KB AdoGUID.mdb               80KB AdoGUID.vbp                2KB Readme.txt                 4KB

Microsoft Access has a ReplicationID AutoNumber field that is a 16-byte (128 bit) Globally Unique Identifier (GUID) that uniquely identifies each record in the database. Please reference the sample project for the code that demonstrates how to SELECT specific GUIDs and Insert GUIDs using the AutoNumber field with Microsoft Access. The following function is a code snippet from the sample that demonstrates how to SELECT a specific GUID from an Access table using Microsoft ActiveX Data Objects (ADO):

Sample Code
Sub AccessReQueryADO

On Error GoTo ErrorMessage

Dim adoCn As adoDb.Connection Dim adoRs As adoDb.Recordset Dim strCn As String Dim strSQL As String

strCn = App.Path & "\adoGUID.mdb"

Set adoCn = New adoDb.Connection With adoCn .Provider = "Microsoft.JET.OLEDB.3.51" .CommandTimeout = 500 .ConnectionTimeout = 500 .Open strCn, "admin", "" End With

If Option7.Value = True Then strSQL = "SELECT * FROM GUIDtable WHERE " & _ "Instr(1,[colGUID],'" & strGUID & "')" Else strSQL = "SELECT * FROM GUIDtable" End If

Set adoRs = New adoDb.Recordset With adoRs Set .ActiveConnection = adoCn .LockType = adLockOptimistic .CursorLocation = adUseServer .CursorType = adOpenForwardOnly End With

adoRs.Open strSQL

txtMessage.Text = ""

While Not adoRs.EOF txtMessage.Text = txtMessage.Text & _ adoRs.Fields("colGUID").Value & " |  " txtMessage.Text = txtMessage.Text & _ adoRs.Fields("colDescription").Value & vbCrLf adoRs.MoveNext Wend

GoTo ExitSub

ErrorMessage: MsgBox Err.Number & " : " & vbCrLf & Err.Description

ExitSub: Label6.Caption = "- ReQueried AccessADO GUID Table..." Set adoCn = Nothing Set adoRs = Nothing

End Sub

Unlike SQL 6.5, SQL 7.0 supports a GUID datatype known as UNIQUEIDENTIFIER. This datatype is a 16-byte GUID stored in the same format as the Microsoft Access AutoNumber (GUID) datatype. There are subtle differences concerning how to Insert and Retrieve the GUIDs among the different database engines. Since SQL 6.5 does not support a native GUID datatype the methods used for storing/retrieving GUIDs are much different than SQL 7.0 or Microsoft Access. SQL 7.0 with the OLEDB provider is almost the same as Microsoft Access with or without the OLEDB provider (SQLOLEDB), as you will see in the sample code. With SQL 6.5 you must store the GUID as a VarBinary(16) datatype. Consequently, to retrieve the GUID with SQL65 you must use a stored procedure and build a Command object with the appropriate ByteArray parameter to pass to the stored procedure SELECT statement.

NOTE: You must use the same code techniques with SQL 7.0 as with SQL 6.5 if you are using the ODBC provider (MSDASQL) since in ODBC 3.51 and below the GUID datatype is not recognized.

The 16-byte (128 bit) data structure of a GUID: typedef struct _GUID {      unsigned long        Data1; unsigned short      Data2; unsigned short      Data3; unsigned char       Data4[8]; } GUID;   * Data1 An unsigned long integer data value. * Data2 An unsigned short integer data value. * Data3 An unsigned short integer data value. * Data4 An array of unsigned characters. To demonstrate GUIDs with SQL 7.0 or SQL 6.5 in the sample project you must specify a valid (test) SQL 7.0/SQL 6.5 server and database. To do so, navigate to the Connection Info tab and change the Server and Database reference. The defaults are (local) Server and the Pubs database. Also, to use the native GUID datatype for SQL 7.0, you must change to the OLEDB provider (SQLOLEDB) by clicking the appropriate option button in the Provider frame at the top of the Form. If you select ODBC as the provider for SQL 7.0 then the application uses the same code as with SQL 6.5.

NOTE: The Connection Info tab has no bearing on Microsoft Access. The default database for Microsoft Access is included with the sample project AadoGUID.mdb as should reside in the Application path.

For each database you select in the sample project you must run Create Table to create the GUID test table and then Insert to automatically generate some test GUID data before running a ReQuery.

NOTE: CoCreateGUID is called in the Insert sample code to generate the test GUID values.

In the sample application there is a ByteArray2GUID function that is used to convert the VarBinary(16) byte array to a GUID string for display. Also, the function is used to convert the GUID string to a byte array for storage in the SQLServer VarBinary(16) datatype column. Note that the function is needed when using the GUIDs interchangeably between Microsoft Access and SQL 6.5. If you Export the Microsoft Access table to SQL 6.5 you will see that the bytes are not stored in the same order in which they display in the Microsoft Access table view. For example:     Reversed...        Not Reversed... ><|>---<  20C68F83-9593-0011-BFBB-00C04F8F8347 'SQLServer view after table Export. 838FC620-9395-1100-BFBB-00C04F8F8347 'Microsoft Access view. NOTE: The bytes are in (DWord and Word) reverse order after Exporting the Microsoft Access table.

Because the Microsoft Access Upsizing Wizard results in the same storage of the bytes in SQL 6.5, you must use the ByteArray2GUID and GUID2ByteArray functions to remain compatible with the storage of the GUIDs in Microsoft Access. If you do not need to Export the Microsoft Access table to SQL 6.5 or upsize the Microsoft Access database to SQL 6.5 then you need only store the bytes in a straightforward fashion.

The following is a code snippet from the code sample that demonstrates the storage of the GUID in the byte format of Microsoft Access.

Sample Code
Sub SQL65InsertGUID

'Insert GUID record. On Error GoTo ErrorMessage

Dim adoCn As adoDb.Connection Dim adoRs As adoDb.Recordset Dim strGUIDtmp As String Dim bytGUID As Byte Dim strCn As String Dim strSQL As String

strCn = "Provider=" & strProvider & _ ";Driver={SQL Server}" & _ ";Server=" & txtServer & _ ";Database=" & txtDatabase & _ ";Uid=" & txtUserID & _ ";Pwd=" & txtPassword

Set adoCn = New adoDb.Connection With adoCn .ConnectionString = strCn .CommandTimeout = 500 .ConnectionTimeout = 500 .Open End With

strGUIDtmp = strGUID

bytGUID = GUID2ByteArray(FilterGUID(strGUIDtmp))

strSQL = "SELECT * FROM GUIDtable WHERE 1=0"

Set adoRs = New adoDb.Recordset With adoRs Set .ActiveConnection = adoCn .LockType = adLockOptimistic .CursorLocation = adUseServer .CursorType = adOpenForwardOnly End With

adoRs.Open strSQL

adoRs.AddNew adoRs.Fields("colGUID").Value = bytGUID adoRs.Fields("colDescription").Value = "This is a test GUID" adoRs.Update

GoTo ExitSub

ErrorMessage: MsgBox Err.Number & " : " & vbCrLf & Err.Description

ExitSub: Label6.Caption = "[ASCII 176] Inserted SQL65 GUID Record..." Set adoCn = Nothing Set adoRs = Nothing

End Sub

'======================  Function GUID2ByteArray(ByVal strGUID As String) As Byte

Dim i As Integer Dim j As Integer Dim sPos As Integer Dim OffSet As Integer Dim sGUID(0 To 2) As Byte Dim bytArray As Byte

ReDim bytArray(0 To 15) As Byte

sGUID(0) = 7 sGUID(1) = 11 sGUID(2) = 15

OffSet = 0 sPos = 0

'AABBCCDD-AABB-CCDD-XXXX-XXXXXXXXXXXX 'Microsoft Access view. 'DDCCBBAA-BBAA-DDCC-XXXX-XXXXXXXXXXXX 'SQLServer view. 'Need to loop through to build the GUID byte array in the Microsoft 'Access storage format since the first eight bytes are reversed. For i = 0 To UBound(sGUID) For j = sGUID(i) To (OffSet + 1) Step -2 bytArray(sPos) = "&H" & Mid$(strGUID, j, 2) sPos = sPos + 1 Next j     OffSet = sGUID(i) Next i

For i = 17 To 31 Step 2 bytArray(sPos) = "&H" & Mid$(strGUID, i, 2) sPos = sPos + 1 Next i

GUID2ByteArray = bytArray

End Function

