Conceptual and Logical Data Design Flashcards

What is a candidate key?

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

A candidate key is a minimal set of attributes (one or more columns) that can uniquely identify every row in a table, from which the primary key is chosen.

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

Answer: A one-to-many relationship between the two entities

The 1:M notation indicates a one-to-many relationship where one instance of the first entity can relate to many instances of the second.

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

Answer: Creating an associative (bridge/intersection) entity

A many-to-many relationship is resolved by introducing an associative entity that holds the foreign keys of both related entities and may include relationship-specific attributes.

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

Answer: Data lineage map / data mapping document

A data mapping document (or lineage map) traces each source field to its target attribute, documenting transformations, business rules, and data origin.

What is denormalization, and when is it appropriate?

Answer: Reversing normalization by intentionally adding redundancy to improve read performance

Denormalization intentionally introduces redundancy into a data model to improve query read performance, typically used in data warehouses or high-read OLAP systems.

What does referential integrity enforce in a relational data model?

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

Referential integrity ensures that foreign key values always correspond to an existing primary key in the referenced table, preventing orphaned records.