DMC Conceptual and Logical Data Design 2

Question 1

What is a candidate key?

Accepted Answer

A minimal set of attributes that uniquely identifies each row in a relation

Answer

Any column with a NOT NULL constraint

Answer

A foreign key candidate waiting to be promoted

Answer

An index created during physical design

Question 2

In an ERD, what does the notation '1' on one side and 'M' on the other side of a relationship line indicate?

Accepted Answer

A one-to-many relationship between the two entities

Answer

The number of attributes in each entity

Answer

The storage size difference between entities

Answer

The number of indexes on each table

Question 3

What technique is used in logical modeling to resolve a many-to-many relationship?

Accepted Answer

Creating an associative (bridge/intersection) entity

Answer

Adding a NOT NULL constraint

Answer

Splitting the relationship into two recursive ones

Answer

Adding a composite index

Question 4

Which design artifact maps source data fields to target data model attributes?

Accepted Answer

Data lineage map / data mapping document

Answer

Data flow diagram

Answer

Physical schema diagram

Answer

Network topology chart

Question 5

What is denormalization, and when is it appropriate?

Accepted Answer

Reversing normalization by intentionally adding redundancy to improve read performance

Answer

Removing all primary keys to reduce constraint overhead

Answer

Converting a logical model to a physical model

Answer

Adding NULL columns to avoid schema changes

Question 6

What does referential integrity enforce in a relational data model?

Accepted Answer

That a foreign key value must match an existing primary key value in the referenced table

Answer

That all attributes have non-NULL values

Answer

That every table has at least one index

Answer

That queries return consistent results under concurrent access