NEWSEQUENTIALID()

Creates a GUID that is greater than any GUID previously generated by this function on a specified computer since Windows was started. After restarting Windows, the GUID can start again from a lower range, but is still globally unique. When a GUID column is used as a row identifier, using NEWSEQUENTIALID can be faster than using the NEWID function. This is because the NEWID function causes random activity and uses fewer cached data pages. Using NEWSEQUENTIALID also helps to completely fill the data and index pages.




If privacy is a concern, do not use this function. It is possible to guess the value of the next generated GUID and, therefore, access data associated with that GUID.

NEWSEQUENTIALID() can only be used with DEFAULT constraints on table columns of type uniqueidentifier. For example:

CREATE TABLE myTable (ColumnA uniqueidentifier DEFAULT NEWSEQUENTIALID())