问题
单项选择题
关系数据库是用( )来表示实体之间的联系。
A．树结构
B．二维表
C．线性表
D．网状结构
答案
参考答案：B
解析： 关系数据库是用二维表来表示实体之间的联系。一个关系是一张二维表，每个关系有一个关系即二维表名。每个数据库文件对应一个二维表格，表示一个关系，表中的每一行表示一个记录，每一列表示一个字段。
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关系数据库是用( )来表示实体之间的联系。
A．树结构
B．二维表
C．线性表
D．网状结构
参考答案：B
解析： 关系数据库是用二维表来表示实体之间的联系。一个关系是一张二维表，每个关系有一个关系即二维表名。每个数据库文件对应一个二维表格，表示一个关系，表中的每一行表示一个记录，每一列表示一个字段。
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| I was cute, active, happy…until that day when I was 15 months old. I had a bad fall. I 1 on a glass rabbit and it cut my eye badly enough to blind it. The doctor said that if the eye was taken out, my face would become out of 2 , so my scarred (有疤痕的), blind and grey eye lived on with me. People often asked uncomfortable questions about my eye or 3 played jokes on me. When the kids played games, I was always the " 4 guy." I 5 imagining that everyone looked down on me. Yet every time Mom noticed I was unhappy, she would say to me, "Hold your head up high and face the world." It helped me move on in life. As a child, I thought Mom meant, "Be careful or you will fall down or knock into something 6 you are not looking." As a teenager, I always looked down to hide my shame (自卑), but I found that people 7 me when sometimes I held my head up high. In high school I was even made monitor, but 8 I still felt like a freak (怪物). All I really wanted was to look like 9 . When things got really bad, I would cary to my mom and she 10 look at me with loving eyes and say, "Hold your head up high and face the world. Let them see the 11 that is inside." That is 12 Mom taught me pride. Mon's love and encouragement gave me the confidence to remove my own doubt. 13 I was able to look people in the eye. I learned not only to appreciate (欣赏) myself but to have deep love for others. "Hold your head up high" has been 14 many times in my home. Each of my children has felt its 15 .The gift she gave me lives on in my children. | ||||
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