I would not recommend taking the approach suggested by Kaushai as it's not a supported procedure - for example that sequence no longer exists in the latest versions of the product.
Why are you trying to alter the order id?
We have some requirement to clean the UAT environment so that it can be used as fresh production environment.
So we need to purge the database completely and also we need to set the order id sequence back to i.e 1.
Edited by: Harry on Nov 3, 2012 9:10 PM