DA0-002 Data Concepts and Environments Practice Question
A data analyst is working with a dataset that includes customer names, email addresses, and purchase history. The analyst wants to ensure that each customer is uniquely identified. Which TWO database concepts should be used to enforce uniqueness and link related data?
⚠ Common exam trap
Candidates often confuse normalization with a constraint or think an index enforces uniqueness, when only primary and foreign keys provide the required referential integrity and unique identification.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Foreign key
A primary key uniquely identifies each row in a table, ensuring no duplicate customer records. A foreign key links related data across tables by referencing the primary key of another table, enforcing referential integrity. Together, they guarantee uniqueness and enable relational joins between customer and purchase history tables.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Foreign key
Why this is correct
A foreign key links related data by referencing the primary key of another table, enforcing referential integrity between customer records and their purchase history. Combined with a primary key, which uniquely identifies each customer, it satisfies the stem's requirement to enforce uniqueness and link related data.
- ✗
Normalization
Why it's wrong here
Normalization organises tables to reduce redundancy and anomalies; it does not itself enforce uniqueness or link records. A primary key enforces uniqueness and a foreign key links related tables. Normalisation is the right choice when designing schema structure to eliminate repeating groups and update anomalies.
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View
Why it's wrong here
A view is a stored query presenting data from underlying tables; it enforces neither uniqueness nor referential links. Primary and foreign keys provide those guarantees. Views suit scenarios requiring a reusable, filtered or joined presentation of existing data without altering the base schema.
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Primary key
Why this is correct
A primary key enforces uniqueness by prohibiting duplicate or null values in its column, guaranteeing each customer row is uniquely identified. This satisfies the stem's requirement to distinguish customers, while foreign keys handle the linking of related purchase data.
- ✗
Index
Why it's wrong here
An index accelerates lookups but does not enforce uniqueness unless declared UNIQUE, and it cannot link tables at all. It is tempting because indexes are commonly created on customer identifier columns, yet the scenario requires a primary key for uniqueness plus a foreign key for relationships.
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