Which values are NOT permitted to be part

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问题单项选择题

Which values are NOT permitted to be part of the primary key

A．alpha-numeric characters

B．punctuation

C．special characters

D．NULL

答案

参考答案：D

阅读理解

阅读对话，判断正(T)误(F)。

Dad: Which dog do you like?

John: I like the black dog. It is taller than the white one.

Dad: Do you like the shorter brown one?

John: I think I like the taller dog. It's stronger.

Dad: I like the white dog. It's younger. Its tail is 6 cm long.

John: The black dog is taller than the brown one. I think it is 30 cm tall.

Dad: I think the brown dog is only 20 cm tall.

John: Can I get a new dog? I'm older now. .

Dad: No, you have two dogs already!

( ) 1. John likes the black dog.

( ) 2. The black dog is taller than the white one.

( ) 3. The black dog is taller than the brown one.

( ) 4. The brown dog is only 30 cm tall.

( ) 5. John doesn't like the taller dog.

名词解释

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