The database can assign sequence Numbers to each node so that it knows the position of each node and can compare the document order of two nodes in constant time.
数据库可以为每个节点分配顺序号，这样就知道每个节点的位置，可以在常数时间内比较两个节点的文档顺序。
2
All of this is fine, but the real value of directly manipulating a cursor is the ability to update the database at a particular position.
上述这些游标都很有用，但是，直接操纵游标的实际价值在于在特定位置更新数据库的能力。
3
With this system, certain vehicles' real-time status, such as gasoline consumption, load and position, can be monitored and sent to a national database.