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【单选题】
创建表时,不允许某列的值为空可以使用( )。A.
NOT NULL
B.
NOT BLANK
C.
NO NULL
D.
NO BLANK
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知识点：
皮皮学刷刷变学霸
举一反三
【单选题】关于阿贝折射仪的使用,不正确的是( )。
A.
需要通过测量蒸馏水的折射率进行校正
B.
蒸馏水的折射率为0%
C.
使用结束后需用蒸馏水擦洗两面棱镜
D.
可用于半粘稠样品测定
【单选题】The fiddler crab is like a clock because it changes colour ______.
A.
in a regular 24—hour rhythm
B.
in answer to the sun’s rays
C.
at low tide
D.
every fifty minutes
【简答题】B The fiddler crab (蟹) is a living clock. It indicates the time of day by the colour of its skin, which is dark by day and pale by night. The crab’s changing colour follows a regular twenty-four hour ...
【简答题】关于期货合约的标准化的意义，下列描述正确的有（ ） 。
【单选题】Not only ______________ vital for reducing fever and helping stop pain, but there are also other things that aspirin can help with.
A.
aspirin has proved
B.
aspirin proved
C.
has aspirin proved
D.
did aspirin prove
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