Any substitutes for MSSQL TimeStamp and GUID types in Oracle?

We are devloping a new database application using MSSQL 7.0 as the back end and we'd like to design the database to allow us to run against an Oracle database with no changes to the VB code and as few changes as possible to the SQL code. I've become quite fond of the MSSQL datatype TimeStamp for concurrency control and the GUID (Globally Unique IDentifier) type for keys so I don't have worry about duplicating values across servers.

As I've discovered there are no corresponding types in Oracle. I think I can get around the GUID problem by creating it in VB code instead of SQL, and storing it as a string in Oracle, but the TimeStamp is another issue. I suppose I could use a Date type column and assume the one second granularity will be enough, but I'd rather have a mechanism I could use in a single column with no holes in it at all.

I'd love to hear from anyone that has tackled either or both issues, or a referal to a source on information. Received on Sun Aug 13 2000 - 00:00:00 CDT