alleryStart learning →By default, which attribute cannot take NULL values?
AThe plain key
BThe paired key
CThe parent key
DThe primary key
Answer & Solution
Correct answer: D. The primary key
1. NULL is allowed in most columns unless forbidden.
2. One attribute is excepted without being asked.
3. By default, each attribute can take NULL values except for the primary key.
4. So the answer is the primary key.
_Source: syllabus Computer Science, Ch 9 'Structured Query Language (SQL)'_
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