DS0-001 Database Structures And SQL Practice Question
A business user needs to calculate the average age of customers, but some age fields are NULL. Which function should be used to treat NULL as 0?
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
✓
COALESCE
The COALESCE function returns the first non-null expression in the list, allowing NULLs to be replaced with 0.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
NULLIF
Why it's wrong here
NULLIF returns NULL if two expressions are equal.
- ✗
IFNULL
Why it's wrong here
IFNULL is vendor-specific (MySQL).
- ✓
COALESCE
Why this is correct
COALESCE is the standard SQL function for handling NULLs.
- ✗
ISNULL
Why it's wrong here
ISNULL is vendor-specific (T-SQL) and less portable than COALESCE.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official CompTIA exam blueprint
This DS0-001 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 DS0-001 exam.