FC0-U71 Data and Database Fundamentals Practice Question
A database administrator wants to enforce that every record in the 'Orders' table must have a non-null unique value in the 'OrderID' column. Which database concept ensures this?
⚠ Common exam trap
Many candidates confuse the four integrity types — candidates often pick 'referential integrity' because it sounds like it governs relationships/records, but the question's keywords 'non-null unique value in a column' point specifically to entity integrity (primary key), not foreign key relationships.
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
✓
Entity integrity
Entity integrity requires that every row in a table be uniquely identifiable by a primary key, which by definition cannot be NULL and must be unique. Enforcing a non-null, unique value in the 'OrderID' column is exactly the definition of entity integrity, typically implemented via a PRIMARY KEY constraint. This ensures each record represents a distinct, identifiable entity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Referential integrity
Why it's wrong here
Referential integrity governs relationships between tables, ensuring a foreign key value matches an existing primary key in the parent table. It says nothing about uniqueness or nullability within the Orders table itself. Referential integrity would be the correct concept if the requirement concerned linking Orders to a Customers table.
- ✓
Entity integrity
Why this is correct
Entity integrity requires every row to have a unique, non-null primary key, so the OrderID column must contain a distinct value in each record. Referential integrity instead governs foreign-key relationships between tables, which the stem does not describe.
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Input validation
Why it's wrong here
Input validation checks data at the application layer before it reaches the database, so it cannot guarantee the constraint for every record — direct inserts, imports and other applications bypass it. Entity integrity, enforced by a primary key or unique NOT NULL constraint, guarantees it at the database. Input validation suits form-level format checking.
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Domain integrity
Why it's wrong here
Domain integrity constrains the values a column may hold — data type, format and permissible range — not uniqueness or nullability of a key. The requirement describes an entity integrity constraint, enforced by a primary key or unique NOT NULL constraint. Domain integrity would be the correct concept for validating that, say, an OrderDate column holds valid dates.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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