CommandBuilder cb = new CommandBuilder(sess, "SELECT x.id FROM Person x", null);
RootPanel.get().add(cb);
Select s = cb.getSelect();
Comparison c = s.addFirstCondition();
s.fireDirty();
ExpressionColumn left2 = (ExpressionColumn) c.getLeft();
left2.updateColumn("X", sess.getDatabase().getMainSchema()
.findTableOrView("PERSON").getColumn("owner"));
c.fireDirty();