Data Modeling Flashcards
7 cards from real 1Z0-006 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Data Modeling flashcards as text
In data modeling terminology, what is a 'candidate key'?
Answer: A minimal set of attributes that can uniquely identify every row in a table
A candidate key is any minimal set of attributes that uniquely identifies each row; one candidate key is chosen as the primary key, and the rest become alternate keys.
What does 'participation constraint' (also called 'existence dependency') define in an ERD?
Answer: Whether every entity instance must participate in a relationship (total) or may optionally participate (partial)
Participation constraints specify whether all (total/mandatory) or only some (partial/optional) entity instances must be involved in a relationship.
A PRODUCT table has columns: ProductID, CategoryID, CategoryName, Price. CategoryName depends on CategoryID, not directly on ProductID. Which normal form violation does this represent?
Answer: 3NF violation due to a transitive dependency
CategoryName transitively depends on ProductID through CategoryID (ProductID → CategoryID → CategoryName), which violates 3NF.
Which modeling concept does an ERD's 'IS-A' (generalization/specialization) hierarchy represent?
Answer: An inheritance relationship where subtypes share attributes of a supertype
An IS-A hierarchy represents generalization/specialization, where subtypes (e.g., HOURLY_EMPLOYEE) inherit common attributes from a supertype (e.g., EMPLOYEE) and add their own specific attributes.
What is a 'natural key' in database design?
Answer: An identifier derived from existing real-world data attributes that naturally uniquely identifies a row
A natural key uses real-world data (such as a Social Security Number or ISBN) that inherently and uniquely identifies an entity.
When should you consider denormalization in a database design?
Answer: To improve read query performance by intentionally introducing controlled redundancy
Denormalization intentionally introduces redundancy to reduce costly joins, improving read performance in data warehouse or reporting scenarios at the cost of some update complexity.
In Boyce-Codd Normal Form (BCNF), what must be true of every functional dependency X → Y?
Answer: X must be a superkey of the table
BCNF requires that for every non-trivial functional dependency X → Y, X must be a superkey, making BCNF stricter than 3NF.