The answer is both a foreign key constraint and a trigger. A foreign key directly enforces referential integrity by ensuring that every CustomerID in the Orders table matches an existing CustomerID in the Customers table, automatically rejecting any orphaned records. A trigger, on the other hand, achieves the same goal through procedural logic—it can be programmed to check the Customers table before an INSERT or UPDATE on Orders and roll back the transaction if the CustomerID is missing, providing a flexible alternative when a formal foreign key isn’t desired. On the CompTIA ITF+ FC0-U61 exam, this tests your understanding of how relational databases maintain data consistency, often appearing as a multiple-choice question where you must recognize that both methods are valid. A common trap is assuming only the foreign key works, but remember that triggers can mimic constraints through custom validation. Memory tip: “Key locks the link, trigger checks the brink.”
FC0-U61 Database Fundamentals Practice Question
This FC0-U61 practice question tests your understanding of database fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A database designer wants to enforce that a 'CustomerID' value in an 'Orders' table must exist in the 'Customers' table. Which TWO methods can achieve this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a trigger to check existence
Option C is correct because a trigger can be programmed to check, before an INSERT or UPDATE on the Orders table, whether the new CustomerID exists in the Customers table. If the value is not found, the trigger can roll back the transaction, enforcing referential integrity without using a formal foreign key constraint. This is a valid method in database systems that support procedural logic within triggers.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Create a unique constraint on Orders.CustomerID
Why it's wrong here
Ensures no duplicates, not existence.
✗
Create an index on Orders.CustomerID
Why it's wrong here
Index improves performance, does not enforce.
✓
Use a trigger to check existence
Why this is correct
A trigger can validate the CustomerID.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a primary key on Customers.CustomerID
Why it's wrong here
Ensures uniqueness but not reference.
✓
Create a foreign key from Orders.CustomerID to Customers.CustomerID
Why this is correct
Foreign key enforces referential integrity.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a primary key or unique constraint with referential integrity, thinking that ensuring uniqueness in the parent table automatically enforces existence in the child table, but neither does so without an explicit foreign key or trigger.
Detailed technical explanation
How to think about this question
Under the hood, a foreign key constraint (Option E) creates a referential integrity rule that the database engine enforces automatically during DML operations, typically using a shared lock or check on the parent table. Triggers (Option C) offer more flexibility, allowing custom error messages or complex validation logic, but they can be slower and are prone to errors if not carefully written. In real-world scenarios, foreign keys are preferred for simplicity and performance, while triggers are used when cross-database or conditional referential integrity is needed.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the FC0-U61 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Database Fundamentals — This question tests Database Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a trigger to check existence — Option C is correct because a trigger can be programmed to check, before an INSERT or UPDATE on the Orders table, whether the new CustomerID exists in the Customers table. If the value is not found, the trigger can roll back the transaction, enforcing referential integrity without using a formal foreign key constraint. This is a valid method in database systems that support procedural logic within triggers.
What should I do if I get this FC0-U61 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company's customer database contains a table named 'Orders' with columns: OrderID, CustomerID, ProductID, Quantity, OrderDate. The company wants to enforce that every CustomerID in 'Orders' must exist in the 'Customers' table. Which database constraint should be added to the 'Orders' table?
medium
A.Check constraint on CustomerID
B.Primary key on CustomerID
✓ C.Foreign key on CustomerID referencing Customers
D.Unique constraint on CustomerID
Why C: A foreign key constraint on CustomerID referencing the Customers table ensures referential integrity. Option A is incorrect because a primary key is for the table's own unique identifier. Option B is incorrect because a unique constraint prevents duplicates but does not reference another table. Option D is incorrect because a check constraint validates data within the same row, not across tables.
Last reviewed: Jun 25, 2026
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