A _____ indicates an absent value that may exist but be unknown or that may not exist at all.
A. Empty tuple
B. New value
C. Null value
D. Old value
Answer:A
A _____ indicates an absent value that may exist but be unknown or that may not exist at all.
A. Empty tuple B. New value C. Null value D. Old value
Explanation:None. 2. If the attribute phone number is included in the relation all the values need not be entered into the phone number column . This type of entry is given as