Multiple choice

By which integrity rule does the number key attribute of a row may be null?

  1. Referential integrity rule

  2. Distinct rows in a table

  3. Entity integrity rule

  4. None of these

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

(A Primary Key or part of it can not be null) - the rule says that 'null' is a special value in a relational database and it does not mean blank or zero.