A            indicates an absent value that may exist but be unknown or that may not exist at all.

Related MCQs

• The predicate in a where clause can involve Boolean operations such as and. The result of true and unknown is               false and unknown is            while unknown and unknown is            
• The result of           unknown is unknown.
• Every time attribute A appears, it is matched with the same value of attribute B, but not the same value of attribute C. Therefore, it is true that:
• An                          consists of a search-key value and pointers to one or more records with that value as their search-key value.
• An ____________ consists of a search-key value and pointers to one or more records with that value as their search-key value.
• Which of the following case does not exist in complexity theory
• Which of the following database object does not physically exist?
• Which one of the following deletes all the entries but keeps the structure of the relation.
• In domain relaional calculus “there exist”
• A dependency exist between two columns when