问题
单项选择题 共用题干题
关系R、S如表4-48所示，R÷（πA1，A2（σ13（S）））的结果为（1），左外连接、右外连接和完全外连接的元组个数分别为（2）。
空白（1）处应选择（）
A.{d}
B.{c，d}
C.{c，d，g}
D.{（a，B.，（b，A.，（c，D.，（d，F.}
答案
参考答案：A
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关系R、S如表4-48所示，R÷（πA1，A2（σ13（S）））的结果为（1），左外连接、右外连接和完全外连接的元组个数分别为（2）。
空白（1）处应选择（）
A.{d}
B.{c，d}
C.{c，d，g}
D.{（a，B.，（b，A.，（c，D.，（d，F.}
参考答案：A
I was brought up by my grandparents for the first years of my life. We 36 in a very small community and all of my aunts and uncles lived 37_ . Everyone had a hand in taking care of my safety. Of course in those days 38 everyone in the community spoke the beautiful language of my childhood. When my grandfather spoke I would _ 39_ him carefully. Then at age six my father 40 from the army. I was forbidden to speak that 41 ever again. My grandfather was 42 . He couldn’t speak English, so my grandmother would 43 for him whenever he spoke to me. With my mother and father we 44 from that small community. I was about to enter public school so I had to learn English. My grandfather 45 when I was eight and we returned to that small community for his funeral. He was 46 in the living room, as was the tradition. I went and stood by him and 47 no one was around I spoke to him in a whisper 48 that beautiful language of my childhood. That was the 49 time I spoke those words. Almost fifty years later, _ 50 _ I had forgotten the beautiful language of my childhood, I had the opportunity to 51 a newly written paper of it. On my first look at it I recognized 52 . I must have looked it over several times in the following weeks. Then one day I read out loud a word from my past. I almost cried. I was 53 reading over other words. Words came 54 back to me after all these years. When receiving something from someone, you don’t take it from their hand, rather you let them lay it in your hand. For me it was 55 ---The beautiful language of my childhood was Michif. It was not only a language but also a way of life.
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