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【单选题】
创建基本表时,在建立CHECK约束时,( )。A.
每个字段只能定义一个CHECK约束
B.
每个字段可以定义多个CHECK约束
C.
不能为单独的一个字段定义CHECK约束
D.
一个表中只能定义一个CHECK约束
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【单选题】Television has changed the lifestyle. of people in every industrialized country in the world. In the United States, where sociologists have studied the effects, some interesting observations have been...
A.
advertisers are interested in experimenting with new ideas
B.
it is still at an early stage of development, compared with the radio
C.
the programs have to be developed in the interests of the sponsors for economic reasons
D.
it is controlled by radio companies
【简答题】Canada is a very large country.It is bigger than China.China is the third largest country in the world.Canada is the second largest.It has an area of nearly 10 million sq. km. Canada has a very long c...
【单选题】Being a Chinese, I feel proud of my country and the contributions _________have been made to the world culture.
A.
that
B.
what
C.
it
D.
one
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