DA0-002 Data Acquisition and Preparation Practice Question
An analyst needs to count the number of orders per customer but only for customers who have placed more than 5 orders. Which SQL construct allows filtering after aggregation?
⚠ Common exam trap
DA0-002 often tests the WHERE vs. HAVING distinction by presenting an aggregate filter and tempting candidates to pick WHERE because it is the more familiar filtering clause.
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
✓
HAVING COUNT(*) > 5
HAVING is the SQL clause specifically designed to filter groups after aggregation has been performed by GROUP BY. Because COUNT(*) is an aggregate function, it cannot be evaluated in the WHERE clause, which runs before grouping. HAVING executes after GROUP BY and aggregation, so it can reference aggregate results like COUNT(*) > 5.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
WHERE COUNT(*) > 5
Why it's wrong here
WHERE is evaluated before GROUP BY, so aggregate functions such as COUNT(*) are unavailable at that stage; the query fails. It tempts because WHERE filters rows, but restricting groups by an aggregate value requires HAVING, which runs after aggregation.
- ✗
LIMIT 5
Why it's wrong here
LIMIT restricts the number of returned rows after ordering; it cannot filter groups by an aggregate count. It tempts because it appears to cap results at five, but the requirement needs HAVING with COUNT(*) applied to the grouped customers.
- ✓
HAVING COUNT(*) > 5
Why this is correct
HAVING filters grouped rows after aggregation, unlike WHERE, which filters individual rows before grouping. Because the requirement is to count orders per customer and then retain only those exceeding five, HAVING COUNT(*) > 5 applies the condition to the aggregated count, satisfying the post-aggregation filtering constraint in the stem.
- ✗
ORDER BY COUNT(*) > 5
Why it's wrong here
ORDER BY sorts the result set; it cannot restrict rows, so COUNT(*) > 5 here is a boolean expression evaluated per row for sorting, not a filter. It is tempting because ORDER BY does reference aggregates, but filtering on an aggregate requires HAVING after GROUP BY.
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Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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