题目内容
某数据库中有员工关系E(员工号，姓名，部门，职称，月薪)；产品关系P(产品号，产品名称，型号，尺寸，颜色)；仓库关系W(仓库号，仓库名称，地址，负责人)；库存关系I(仓库号，产品号，产品数量)。 a．若数据库设计中要求： ①仓库关系W中的“负责人”引用员工关系的员工号 ②库存关系I中的“仓库号，产品号”唯一标识I中的每一个记录 ③员工关系E中的职称为“工程师”的月薪不能低于3500元 则①②③依次要满足的完整性约束是______。
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To use it seems so natural to put up an umbrella to keep the water off when it rains. But actually the umbrella was not invented as protection against rain. Its first use was as a shade against the sun! Nobody knows who first invented it, but the umbrella was used in very ancient times. Probably the first to use it were the Chinese, way back in the eleventh century. We know that the umbrella was used in ancient Egypt and Babylon as a sunshade. And there was a strange thing connected with its use: it became a symbol of honor and authority. In the Far East in ancient times, the umbrella was allowed to be used only by royalty or by those in high office. In Europe, the Greeks were the first to use the umbrella as a sunshade. And the umbrella was in common use in ancient Greece. But it is believed that the first persons in Europe to use the umbrella as protection against the rain were the ancient Romans. During the Middle Age, the use of the umbrella practically disappeared. Then it appeared again in Italy in the late sixteenth century. And again it was considered a symbol of power and authority. By 1680, the umbrella appeared in France, and later on in England. By the eighteenth century, the umbrella was used against rain throughout most of Europe. Umbrellas have not changed much in style during all this time, though they have become much lighter. It wasn’t until the twentieth century that women’s umbrellas began to be made, in a whole variety of colors. This passage talks mainly about ______.
Have you eaten too much over the holidays You should try fidgeting for a while. Those around you might not like it, but scratching (moving your nails (指甲) against a part of your body) and twitching (moving suddenly and quickly when you don’ t want to) is an important way of burning up calories (卡路里). American researchers have found that some people’s squirming ( continuously turn your body when nervous) and wigging (move in small movements, especially from side to side) equals (等于) several miles of slow running each day. The scientists, based at the National Institute of Heahh’s laboratory in Phenix, Arizona, are studying why some people get fat and other stay slim. In one study 177 people each spent 24 hours in a room in the institute where the amount (量) of energy is measured by their oxygen and carbon dioxide (二氧化碳) levels. By the end of the day, some people had burned up 800 calories in toe-tapping, (moving the front part of your foot up and down) finger-drumming (hitting your fingers continuously and lightly against something hard) and other nervous habits. However, others had burned up only 100 calories. The researchers found that slim women fidget more than fat women, but there was no significant difference in men. Heavy people burn up more energy when they fidget than thin people do. Scientists think a fidget habit to be ______.
简答题 简述资产阶级革命派的阶级基础和骨干力量。
Technology is the application (应用) of knowledge to production. Thanks to modern technology, we have been able to increase greatly the efficiency of our work force. New machines and new methods have helped cut down time and expense while increasing overall output. This has meant more production and a higher standard of living. For most of us in America, modern technology is thought of as the reason why we can have cars and television sets. However, technology has also increased the amount of food available (可供食用的) to us, by means of modern farming machinery and animal breeding techniques, and has extended our life span via (通过) medical technology. Will mankind continue to live longer and have a higher quality of life In large measure the answer depends on technology and our ability to use it wisely. If we keep making progress as we have over the past fifty years, the answer is definitely yes. The advancement of technology depends upon research and development, and the latest statistics (统计) show that the united States is continuing to pump billions of dollars annually (每年) into such efforts. So while we are running out of some scarce resources (稀缺资源) we may well find technological substitutes (代用品) for many of them through our research programs. Therefore, in the final analysis the three major factors of production (land, labor and capital) are all influenced by technology. When we need new skills on techniques in medicine, people will start developing new technology to meet those needs. As equipment proves to be slow or inefficient, new machines will be invented. Technology responds to our needs in helping us maintain our standard of living. How does "technology" increase the amount of food available to us
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