1Z0-006 Data Modeling 2 — Questions and Answers
Question 1: In an Entity-Relationship diagram, what does a double rectangle around an entity name signify?
- A strong entity with a primary key
- A weak entity that depends on another entity for identification (Correct answer)
- An associative entity linking two others
- A derived entity computed from other attributes
Correct answer: A weak entity that depends on another entity for identification
A double rectangle denotes a weak entity, which cannot be uniquely identified by its own attributes alone and relies on a parent (owner) entity.
Question 2: Which normal form eliminates partial dependencies on a composite primary key?
- First Normal Form (1NF)
- Second Normal Form (2NF) (Correct answer)
- Third Normal Form (3NF)
- Boyce-Codd Normal Form (BCNF)
Correct answer: Second Normal Form (2NF)
2NF removes partial dependencies, ensuring every non-key attribute depends on the whole composite primary key, not just part of it.
Question 3: A CUSTOMER can place zero or many ORDERS, and each ORDER must belong to exactly one CUSTOMER. How is this cardinality expressed?
- Many-to-many between CUSTOMER and ORDER
- One-to-one between CUSTOMER and ORDER
- One (CUSTOMER) to many (ORDER) with mandatory participation on ORDER side (Correct answer)
- Many (CUSTOMER) to one (ORDER) with optional participation
Correct answer: One (CUSTOMER) to many (ORDER) with mandatory participation on ORDER side
This is a one-to-many relationship where ORDER has mandatory participation (must have a customer) and CUSTOMER has optional participation (may have no orders).
Question 4: What is a surrogate key in relational database design?
- A natural key derived from real-world data attributes
- A system-generated artificial key with no business meaning (Correct answer)
- A composite key combining two foreign keys
- A key shared between a parent and child table
Correct answer: A system-generated artificial key with no business meaning
A surrogate key is a system-generated (e.g., auto-increment) identifier with no inherent business meaning, used to uniquely identify rows.
Question 5: In data modeling, what does 'domain' refer to?
- The network address of the database server
- The set of all valid values an attribute can hold (Correct answer)
- A group of related tables in a schema
- The physical storage location of table data
Correct answer: The set of all valid values an attribute can hold
A domain defines the permissible set of values for an attribute, including data type, length, format, and constraints.
Question 6: Which relationship type in an ERD is represented by a line with crow's-foot notation on both ends?
- One-to-one
- One-to-many
- Many-to-many (Correct answer)
- Self-referencing
Correct answer: Many-to-many
Crow's-foot notation on both ends of a relationship line indicates a many-to-many relationship between the two entities.
Question 7: What is the purpose of a junction (bridge) table in relational database design?
- To store indexes for faster query performance
- To resolve a many-to-many relationship into two one-to-many relationships (Correct answer)
- To enforce referential integrity constraints automatically
- To hold temporary data during transaction processing
Correct answer: To resolve a many-to-many relationship into two one-to-many relationships
A junction table sits between two entities in a many-to-many relationship, holding foreign keys to both and converting the relationship into two one-to-many links.
1Z0-006 Data Modeling 2
In an Entity-Relationship diagram, what does a double rectangle around an entity name signify?