uniqueidentifier stores 16-bit GUIDs. uniqueidentifier can be created with newid()
newsequentialid() (however in a default constraint of a table column only)
uniqueidentifer declare
@uid_1 uniqueidentifier,
@uid_2 uniqueidentifier;
set @uid_1 = newid() ; -- compliant with RFC 4122
set @uid_2 = '01234567-89ab-cdef-0123-456789abcdef';
print('uid_1 = ' + convert(varchar(255), @uid_1));
print('uid_2 = ' + convert(varchar(255), @uid_2));