在同一关系上能否对两个不同查找键值建立两个主索引为什么_爱下问搜题

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问题问答题

在同一关系上能否对两个不同查找键值建立两个主索引为什么

答案

参考答案：在同一关系上不允许对两个不同查找键值建立两个主索引，这是因为大多数情况下，主文件的顺序不可能同时与两个索引的查找键值顺序一致。

完形填空

In 1982, Steven Callahan was crossing the Atlantic alone in his sailboat when it struck something and sank. He was out of the sailing track and floating in a lifeboat, alone. His supplies were 36 . His chances of surviving were small. 37 when three fishermen found him seventy-six days later, he was alive — much 38 than he was when he started, but alive.
His 39 of how he survived is interesting and attractive. His subtle act — how he 40 to catch fish, how he evaporated sea water to 41 fresh water — is very interesting. But the thing that 42 my eye was how he managed to keep himself going when all hope seemed lost, when it seemed no 43 continuing the struggle, when he was 44 greatly, when his lifeboat was pierced and after more than a week’s struggling with his weak body. He was starved and 45 exhausted. Giving up would have seemed the only sensible choice.
When people 46 these kinds of circumstances, they do something with their minds that gives them the courage to keep going. Many people in 47 dangerous circumstances give in or go mad. Something the survivors do with their thoughts helps them find the courage to carry on 48 major difficulties.
"I tell myself I can 49 it," wrote Callahan in his book. "Compared to what others have been through, I'm fortunate. I tell myself these things over and over, 50 courage and strength."
I wrote that down after I read it 51 it struck me as something important. And I've told myself the same thing when my own goals seemed 52 off or when my problems seemed too powerful. And every time I've said it, I have always come back to my senses.
The truth is, our circumstances are only bad 53 to something better. But others have been through much worse, that is, in comparison with what 54 have been through, you're fortunate. Tell this to yourself over and over again, and it will help you 55 the rough spots with a little more perseverance(毅力) .

B．imagination

C．instruction

小题9:A improving B. suffering C. strengthening D. increasing

A．for the lack of

B．in spite of

C．in support of

D．as a result of

C．building up

C．contributed

A．see through

B．cut through

C．get through

D．think through

单项选择题

党的各级代表大会的代表和委员会的产生，要体现选举人的意志。选举采用（）的方式。

A.代表表决

B.公开表决

C.无记名投票

D.集体讨论