问题
单项选择题
在关系模型概念中，不含多余属性的超码称为______。
A) 候选码
B) 主码
C) 外码
D) 备用码
答案
参考答案：A
解析： 在关系模型概念中，不含多余属性的超码称为候选码，所以本题的答案为A。
搜题请搜索小程序“爱下问搜题”
在关系模型概念中，不含多余属性的超码称为______。
A) 候选码
B) 主码
C) 外码
D) 备用码
参考答案：A
解析： 在关系模型概念中，不含多余属性的超码称为候选码，所以本题的答案为A。
| 完形填空。 | ||||
| It was Thanksgiving morning and in the crowded kitchen of my small home I was busy preparing the traditional Thanksgiving turkey when the doorbell rang. I 1 the front door and saw two small children in 2 huddling(挤作一团)together on the top step. "Any old 3 , lady ?"asked one of them. I was busy. I wanted to say "no" until I looked down at their feet. They were 4 thin little sandals(凉鞋), wet with heavy snow. "Come in and I'll make you a cup of hot 5 ". They walked over and sat down at the table. Their 6 sandals left marks upon the floor I served them coffee and bread with jam to fight against the cold 7 . Then I went back to the 8 and started again on my household budget. The silence in the front room 9 me, so I looked in. The girl held the 10 cup in her hands, looking at it. The boy asked in a flat 11 ,"Lady, are you rich?" "Am I rich? Mercy, no!"I looked at my shabby slipcovers(破旧的沙发套). The girl 12 her cup back in saucer(茶托)carefully and said, "Your 13 match you saucers. "Her voice was hungry with a need that large amount of food could supply. They left after that, 14 their bundles of papers against the wind. They hadn't said "Thank you". They didn't 15 to. They had reminded me that I had so much for which to be 16 . Plain blue china cups and saucers were 17 worth five pence. But they matched. I moved the chairs back from the fire and cleaned the living room. The muddy 18 of small sandals were 19 wet upon my floor. "Let them be for a while, "I thought. Just 20 I should begin to forget how rich I am. | ||||
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(每小题的备选答案中只有一个最符合题意。)
| 某估价对象原为某单位2000年集资建房，其中土地是由单位出资购买的，经政府批准单位决定6年后才发给职工房地产权证，自发证之日起，房地产才能上市交易。在距离上市还有6个月时，由于债务纠纷，法院判决将估价对象抵债，请评估其价值。 |
评估中估价对象状况应选择( )。
A．集资建房之日
B．距离上市6个月之日
C．法院判决之日
D．发放房地产权证之日