DA0-002 Data Acquisition and Preparation Practice Question
Which SQL aggregate function would an analyst use to calculate the average value of a numeric column?
⚠ Common exam trap
DA0-002 often tests whether candidates confuse AVG with SUM or COUNT, or assume MEDIAN is a standard SQL aggregate, leading them to select a function that returns a total or a count instead of a mean.
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
✓
AVG
The AVG aggregate function computes the arithmetic mean of a numeric column, which is exactly what the analyst needs. It ignores NULL values by default and returns a single average value for the specified column or expression.
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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SUM
Why it's wrong here
SUM adds all values in a numeric column, producing a total rather than a mean. It is tempting because averaging does involve summation, and SUM is frequently used alongside AVG, but the question asks specifically for the average, which AVG computes directly.
- ✓
AVG
Why this is correct
AVG computes the arithmetic mean of a numeric column, directly satisfying the requirement to calculate an average value. Unlike SUM, which totals values, or COUNT, which tallies rows, AVG divides the sum by the count of non-NULL entries, returning the precise average the analyst needs.
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COUNT
Why it's wrong here
COUNT returns the number of rows or non-null values, not a numeric mean. It is tempting because analysts often pair COUNT with other aggregates to check row volumes, but averaging a numeric column requires AVG, which sums values and divides by the count.
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MEDIAN
Why it's wrong here
MEDIAN is not a standard SQL aggregate function in most database engines; it returns the middle value where supported, not the arithmetic mean. It is tempting as a robust alternative to averages, but the question asks for the average value, which AVG calculates.
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Written and reviewed by Johnson Ajibi, MSc IT Security
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Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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