WHERE vs HAVING?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of SQL & Databases conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
| WHERE | HAVING |
|-------|--------|
| Filters rows | Filters groups |
| Executes before GROUP BY | Executes after GROUP BY |
| Cannot use aggregates | Can use COUNT(), SUM(), etc. |
| Can reference any column | Can only reference grouped columns or aggregates |
SELECT department, AVG(salary) AS avg_sal
FROM employees
WHERE hire_date > '2020-01-01' -- Filter rows first
GROUP BY department
HAVING AVG(salary) > 60000; -- Then filter groups
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Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.