DB: Quiz 4 Review

A _______ key is a primary key taken from one table that is placed into another table in order to create a link/relationship between the two tables

Answer explanation

The foreign key's name does not need to match the primary key's name - the relationship just needs to be defined in order to enforce referential integrity

A column in a database table is known as a(n)...

• relation

• attribute

• relationship

• table

Most relationships in a database are

• 1:1

• 1:M

• M:N

A many to many relationship cannot truly exist in a database implementation

• True

• False

Describe the process for altering a many to many relationship into something that can be implemented in a database

Answer explanation

A composite table needs to be created between the two original tables. The primary keys from both tables need to be foreign keys in the new composite table. There will now be 2 1:M relationships -one from each of the original tables to the new composite table. The many side of the relationships will be pointed toward the new composite table.

Which of the following is true about values in a relational database?

• A common data type is a list

• Only multivalued attributes are allowed

• The only 3 data types we typically use are datetime, varchar, and int. All others create redundancy

• Multiple values in a single cell (multivalued attributes) are not allowed

Answer explanation

Multivalued attributes are not allowed in relational database design

Creating an ______ diagram, which details business concepts, information to be stored about each concept, and the relationships between them, is the first step in database design

Another name for a table is ....

• relation

• attribute

• entity

• relationship

Answer explanation

As far as we're concerned, entities, relations, and tables all refer to the same thing

Describe referential integrity

Answer explanation

All values of foreign keys must currently exist as primary keys in the related table. This ensures we're not referencing keys that don't actually exist.

Describe entity integrity

Answer explanation

All entities must have a primary key that never contains a null value and is never duplicated between rows of the table.