This paper analyzes the events independences and incompatibility, and discusses some relations among independence, incompatibility and null events.

对事件的独立性、互不相容性进行了剖析，并讨论了独立性、互不相容性与零概率事件的关系。

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WatchKey poll returns the next WatchKey that has had some of its events occur, or null if no registered events have happened.

如果有相关事件出现，WatchKey poll会返回下一个WatchKey，或者没有注册的事件发生，会返回null。

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Finally, the team needed to assemble everything into a table and update the events table with the depot location name or null. The full SQL is.

最后，该团队需要将每项数据组装到一个表中，使用维修站位置、名称或null更新事件表。

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