Question

is one of the feature of primary key is. it is not null. i have little bit confusion ​

Answer 1

Answer:

primary key is the unique identifier in a table

it can't be null because primary key purpose is to uniquely identify records. If two records of a single column have a NULL value, the column values are not considered equal.

hope this will help you

Answer 2

Some placed degree is defined as The degree of a relationship type concerns the number of entities within each entity type that can be linked by a given relationship type. ... In another context cardinality is a number of rows in table and degree is a number of columns

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