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FC0-U71 Practice Question: A database designer wants to enforce that a…
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?
⚠ Common exam trap
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.
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
✓
Use a trigger to check existence
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.
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.
- ✗
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.
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Senior Network & Security Engineer · founder of Courseiva
This FC0-U71 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the FC0-U71 exam.