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问题 单项选择题

当用SQL语言的ALTERTABLE语句修改基本表时，要删除其中的某个完整性约束条件，应在该语句中使用( )。

A．MODIFY

B．DROP

C．ADD

D．DELETE

答案

参考答案：B

多项选择题

进行性多灶性白质脑病的哪项表述是正确的（）

A. * * 多瘤空泡病毒引起

B.亚急性或慢性起病

C.病程晚期可出现痴呆

D.非特异的弥漫性或局灶性慢波脑电图

E.CT可见白质内多灶性低密度区
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单项选择题

Prior to the UML, there was no clearleading (66) Ianguage. Users had to choose from among many similar modeling languages with minor differences in overall (67) power. Most of the modeling languages shared a set of commonly accepted concepts that are expressed slightly differently in various languages. This lack of (68) discouraged new users from entering the OO market and from doing OO modeling, without greatly expanding the power of modeling. Users longed for the industry to adopt one, or a very few, broadly supported modeling languages suitable for (69) usage.

Some Vendors were discouraged from entering the OO modeling area because of the need to support many similar, but slightly different, modeling languages. In particular, the supply of add-on tools has been depressed because small vendors cannot afford to support many different formats from many differem (70) modeling tools. It is important to the entire OO industry to encourage broadly based tools and vendors, as well as niche products that cater to the needs of specialized groups.

（68）处填（）。

A．agreement

B．understanding

C．characteristic

D．diversity
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