DP-900 Describe core data concepts Practice Question
A company stores customer data in a relational database. The database design includes a rule that every order must be associated with a valid customer ID that exists in the Customers table. This rule is an example of which data concept?
⚠ Common exam trap
Many candidates confuse referential integrity with entity integrity, mistakenly thinking that any rule involving a 'valid ID' is about primary keys, when in fact it is about foreign key relationships between tables.
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
✓
Referential integrity
Referential integrity ensures that relationships between tables remain consistent. In a relational database, a foreign key constraint enforces that every order's customer ID must match an existing customer ID in the Customers table, preventing orphaned records. This rule directly implements referential integrity as defined by the SQL standard (e.g., via FOREIGN KEY constraints).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Referential integrity
Why this is correct
Referential integrity is a database constraint enforced by foreign keys: it guarantees that every value in a foreign key column exactly matches an existing primary key value in the referenced table, thereby preventing orphaned rows. This rule is precisely what the scenario describes—the relational database uses these key relationships to maintain valid associations between customer records and related tables.
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Data normalization
Why it's wrong here
Data normalization is a design methodology that structures tables to minimize redundancy and avoid update, insert, and delete anomalies by decomposing data into well-formed relations. Although normalization can indirectly improve data quality, it does not itself define or enforce the foreign-key-to-primary-key matching rule; that enforcement is a matter of referential integrity constraints, not of normalizing the schema.
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Entity integrity
Why it's wrong here
Entity integrity is a rule that applies within a single table, requiring that each row's primary key be both unique and non-null so that every entity can be uniquely identified. It does not govern relationships between tables, so the described behavior of matching customer data across tables via foreign keys is outside its scope; entity integrity would be violated only by duplicate or missing primary keys, not by unmatched foreign key values.
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Data consistency
Why it's wrong here
Data consistency is a broad principle, often associated with ACID transactions, that ensures a database moves from one valid state to another and that all constraints, triggers, and rules remain satisfied after any operation. The specific mechanism described—using foreign keys to enforce that values in one table correspond to primary keys in another—is a concrete referential integrity constraint, not the general concept of consistency, which encompasses many other validation and atomicity guarantees.
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Data Roles and Core Concepts
Key term
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
Key term
Relational database
A relational database organizes data into tables with rows and columns, where each table relates to others using unique keys, allowing efficient storage, retrieval, and manipulation of structured information.
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