【单选题】【消耗次数：1】
若事务T已对数据表R加上X锁，则另一事务S ( )。
①
A．只能读取表R
②
B．只能修改表R
③
C．能读取和修改表R
④
D．不能读取和修改表R
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【多选题】
若事务T对数据对象A加上S锁，则系列说法正确的是（ ）。
①
事务T可以读A和修改A。
②
事务T可以读A但不能修改A。
③
事务能对A加S锁和X锁。
④
其它事务只能再对A加S锁，而不能加X 锁。
【单选题】
若关系R和S分别有r和s个属性，分别含有m和n个元组，则R×S（ ）
①
A.包含r+s个属性和m+n个元组
②
B.包含r+s个属性和m×n个元组
③
C.包含r×s个属性和m+n个元组
④
D.包含r×s个属性和m×n个元组
【单选题】
若关系R和S分别有r和s个属性，分别含有m和n个元组，则R×S（ ）
①
包含r+s个属性和m+n个元组
②
包含r+s个属性和m×n个元组
③
包含r×s个属性和m+n个元组
④
包含r×s个属性和m×n个元组
【简答题】
用真值表判断公式“((p?q) ù (q?r)) ? (p?r)”的类型:[填空1]
随机题目
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How difficult it is ______ the modern world without oil.
①
imagining
②
imagined
③
to imagine
④
having imagined
【单选题】
The exchange of goodwill mission greatly ______ a better understanding between the two countries.
①
carries out
②
brings around
③
breaks out
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contributes to
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I like this jacket better than that one, but it costs twice ______.
①
as much
②
so much
③
that much
④
too much
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Young drivers under 25 have the highest number of accidents while those over 50 have ______.
①
the less
②
the least
③
the fewer
④
the fewest
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The novelist is a highly ______ person whose works appeal to many readers.
①
imaginable
②
imaginative
③
imaginary
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imagined
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The reason why he didn’t take the exam was _____ he had an accident on his way to the school.
①
because
②
because of
③
that
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due to
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Our Chinese tradition is quite different _____ we only want to defend our own country, not to invade other countries.
①
because
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for
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in that
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that
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Since you have already come, you _____ stay here for a couple of days.
①
might well
②
might as well
③
might have to
④
might
【单选题】
I found the book you recommended in the library, ______ is missing.
①
the front cover of which
②
the front cover of that
③
that front cover
④
of what front cover
【单选题】
Malaysian Airlines lost an airplane on March 8 last year, _____ whereabouts still remains a mystery.
①
its
②
whose
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their
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the