Self Doubt

Question

1.A primary key cannot be NULL (Any of its attributes can’t be NULL)

2.can candidate key be NULL(All attr) (Other than primary keys i,e alternate keys)

3.can some attributes of candidate key be NULL??

which of these are true . false

Comments

in that case candidate key termed as primary key where prime can not be null otherwise it termed as alternate key.

A prime attribute is a part of candidate key where key is primary key.

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can you explain little more about candidate key and alternate keys which can be null and which not ...it so confusing for me :(

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see primary key cant be null ..candidate keys other than  the primary key may be null i.e alternate keys may be null

Answer 1

Primary key cannot be Null but Candidate key apart from Primary key may have Null values