方向和加速表传感器都提供三个数据值。
The orientation and accelerometer sensors each provide three data values.
取决于你今后从事哪个方向的化学研究，你可能会不经意地记住周期表的某一部分，这就够了，但是要注意，你真正需要知道的是如何使用元素周期表。
Depending on what kind of chemistry you go in to, you might accidentally memorize parts of the table, which is fine, but what you really want to know how to do is know how to use the periodic table.
索引的确能增强DB 2查询性能，但如果一个表上放置太多索引，那么最终响应时间和流量将走向错误方向。
Indexes can really turbocharge DB2 query performance, but if you put too many on a table, you could end up with response time and throughput going in the wrong direction.
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