题目内容
1911年10月武昌起义的具体组织和发动的团体有______
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设关系模式R(U，F)，其中R上的属性集U={A，B，C，D，E}，R上的函数依赖集F={A→B，DE→B，CB→E，E→A，B→D)。______为关系R的候选关键字。分解______是无损连接，并保持函数依赖的。 以下关于RDBMS数据分布的叙述中，错误的是______。
下列哪些组织是由孙中山组建的______
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______。
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 ______.
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