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【单选题】
20130258在Access中,下列关于主键的叙述中,不正确的是(58)。A.
主键可以唯一区分表中的每一条记录
B.
每一条记录的主键是不允许重复的，也不允许为空
C.
主键通常只允许用数字表示
D.
多个字段主键也称为组合主键，即主键由多个字段组成
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A.
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B.
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C.
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D.
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【多选题】在汛期，水库、闸坝和其他水工程设施的运用，以下说法正确的是（）。
A.
必须服从有关的防汛指挥机构的调度指挥和监督
B.
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C.
其汛期限制水位以上的防洪库容的运用，必须服从防汛指挥机构的调度指挥和监督
D.
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