Ubercart

Right, the sequences table was removed in Drupal 6. Now you have to adjust the auto_increment value if you have MySQL. I'm not exactly sure how that works with PostgreSQL. I think that column should have some kind of serial index for its primary key.

Nevermind

Found this:

In drupal 6 the sequences table was eliminated, in favor of autoincrement database tables.

So the code for the D6 version of ubercart (using MySQL) is
alter table uc_orders auto_increment = 6858;