INF 214 Quiz 1 Flashcards
The candidate key determines all the other keys:
Why/why not?
True, The candidate key is one key and it is always unique; therefore everything else, the other keys, if any and all attributes can be derived from it.
Functional dependence implies a primary key / foreign key relationship: True
Why/why not?
Functional dependence looks at entity integrity as well as referential integrity. Referential integrity looks at PK/FK relationship.
A composite key has at least one attribute: False
Why/why not?
The word composite means “added together”, so it always has at least two attributes.
A superkey and composite key are synonyms: False
Why/why not?
A composite key consists of two or more keys, whereas a superkey can be either only one attribute or more.
A flag ensures NULL vales are “highlighted”: True
No answer
An Entity Relationship Diagram should avoid redundancy: True
Why/why not?
Although an ERD should avoid redundancy as much as possible, with referential integrity, you will have PK/FK redundancy which cannot be avoided.
Entity integrity looks closely at the primary key / foreign key relationship: False
Why/why not?
Entity integrity looks at the relationship of the PK with all the other attributes of that specific table.
You can use a secondary key in an entity if the table does not have a primary key: False
Why/why not?
All tables have PKs, however, if the PK is there, but unknown, you can search for the data with the secondary key.
A foreign key in another table can have NULL values: True
Why/why not?
A PK must have a unique value, but if used as a FK, it can be either a unique value or NULL.
A NULL value does not cause problems when using functions: False
Why/why not?
It creates problems when performing calculations and one value is NULL.
