. Question 21 Correct All primary key entries are unique , and no part of a primary key may be ____.
. Question 22 Correct Since it is used to link the tables that originally were related in a M : N relationship , the composite entity structure includes — as foreign keys — at least the ____ keys of the tables that are to be linked .
. Question 23 Correct A ____ contains at least all of the attribute names and characteristics for each table in the system .
. Question 24 Correct The ____ constraint can be placed on a column to ensure that every row in the table has a value for that column .
. Question 25 Correct Ideally , an entity identifier is composed of ____ attribute ( s ).
. Question 26 Correct A relationship is an association between ____.
. Question 27 Correct Another word for existence-independent is ____.
. Question 28 Correct If an entity can exist apart from one or more related entities , it is said to be ____ -independent .
. Question 29 Correct Knowing the ____ number of entity occurrences is very helpful at the application software level .
. Question 30 Correct A ____ relationship exists when an association is maintained within a single entity .
. Question 31 Correct A ____ identifier is composed of more than one attribute .
. Question 32 Correct A ____ should be a derived attribute . . Question 33 Correct An atomic attribute ____.
. Question 34 Correct A table that has all key attributes defined , has no repeating groups , and all its attributes are dependent on the primary key , is said to be in ____.