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根据对数据源操作方式和结果的不同，查询可以分为五类：选择查询、交叉表查询、参数查询、______和SQL查询。
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Invisibility Ring Scientists can’t yet make an invisibility cloak like the one that Harry Potter uses. But, for the first time, they’ve constructed a simple cloaking device that makes itself and something placed inside it invisible to microwaves. When a person "sees" an object, his or her eye senses many different waves of visible light as they bounce off the object. The eye and brain then work together to organize the sesensations and reconstruct the object’s original shape. So, to make an object invisible, scientists have to keep waves from bouncing off it. And they have to make sure the object casts no shadow. Otherwise, the absence of reflected light on one side would give the object away. Invisibility isn’t possible yet with waves of light that the human eye can see. But it is now possible with microwaves. Like visible light, microwaves are a form of radiant energy. They are part of the electromagnetic spectrum, which also includes radio waves, infrared light, ultraviolet rays, X rays, and gamma rays. The wave lengths of microwaves are shorter than those of radio waves but longer than those of visible light. The scientists’ new "invisibility device" is the size of a drink coaster and shaped like a ring. The ring is made of a special material with unusual ability. When microwaves strike the ring, very few bounce off it. Instead, they pass through the ring, which bends the waves all the way around until they reach the opposite side. The waves then return to their original paths. To a detector set up to receive microwaves on the other side of the ring, it looks as if the waves never changed their paths as if there were no object in the way! So, the ring is effectively invisible. When the researchers put a small copper loop inside the ring, it, too, is nearly invisible. However, the cloaking device and anything inside it do cast a pale shadow. And the device works only for microwaves, not for visible light or any kind of electromagnetic radiation. So, Harry Potter’s invisibility cloak doesn’t have any real competition yet. Harry Potter’s invisibility cloak doesn’t have any real competition yet, because ______.
有经验的电影剧本作者在创作120页的电影剧本时，通常会交上135页的初稿。正如一位电影剧本作者说的，“这样使那些负责电影的人在接到剧本后有一个机会进行创造，他们至少可以删掉15页”。 以上引用的这位电影剧本作者的论述表达了下面哪个观点
患者，男，2年来阵发心悸，1d前无明显诱因再次发作，伴头晕、乏力、无胸痛，无黑矇晕厥。查体：BP 96/53mmHg，P 160/min，双肺音清，心律齐，未闻及杂音。 对该患者根治方法为
对生活在化工厂附近地区的居民所作的正常医疗检查发现，这些居民在致命器官上受到的可能导致癌变的伤害的百分比相当高。这可能是由于有毒的化学物质从化工厂流入河床而导致的。 以下哪项所提供的信息为确定化工厂对可能出现癌变的当地居民是否应当负责任最有用
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