hardMultiple ChoiceObjective-mapped
FC0-U71 Practice Question: A query uses a LEFT JOIN between Customers and…
A query uses a LEFT JOIN between Customers and Orders. The result set includes customers with no orders. What does the Orders columns show for those customers?
⚠ Common exam trap
Candidates often confuse NULL with zero or an empty string, thinking a missing record should show a default value like 0 or '', but SQL strictly uses NULL to represent the absence of a matching row in a LEFT JOIN.
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
✓
NULL
In a LEFT JOIN, all rows from the left table (Customers) are retained, and for rows with no matching rows in the right table (Orders), the columns from the right table are filled with NULL. This is the standard SQL behavior defined by the SQL standard (ISO/IEC 9075). Therefore, for customers with no orders, the Orders columns show NULL, not zero, an empty string, or any other default value.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
NULL
Why this is correct
LEFT JOIN produces NULL when no match.
- ✗
The same as the customer ID
Why it's wrong here
No, it's NULL.
- ✗
Zero
Why it's wrong here
NULL is used to indicate missing data, not zero.
- ✗
Empty string
Why it's wrong here
NULL is used, not empty string.
Go deeper
Related to this question
About these practice questions
This FC0-U71 question is part of Courseiva's 988-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
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.