Beginner~2h
Aggregations & Grouping in SQL & DatabasesInterview Readiness Check
GROUP BY, HAVING, COUNT/SUM/AVG with NULLs, and conditional aggregation patterns.
group byhavingcountsumavgaggregateconditional aggregation
Learning path
Joins & Relationships→Aggregations & Grouping ← you are here→Window FunctionsCTEs & Recursive QueriesSubqueries & EXISTS
Try a sample question
What is the difference between WHERE and HAVING?
A.WHERE filters rows before grouping; HAVING filters groups after aggregation
B.WHERE filters after grouping; HAVING filters before grouping
C.HAVING is faster than WHERE on large tables
D.WHERE cannot use indexed columns; HAVING can
Sign up free to take the full check and see the answer with an explanation.
What this module tests
- Conceptual understanding of aggregations & grouping fundamentals
- Trade-offs and design decisions in real system scenarios
- group by and having — applied knowledge
- Interview-style reasoning and explanation quality
Free to start
Take the Aggregations & Grouping check →
10 questions · Dimension scoring · AI coach feedback · Shareable result
Test your knowledge — free →No credit card · Takes 10–15 min
Frequently asked questions
- What does the Aggregations & Grouping check test?
- The check covers group by, having, count/sum/avg with nulls, and conditional aggregation patterns. Questions span beginner to advanced difficulty and test both conceptual understanding and practical trade-off reasoning.
- What keywords should I know for Aggregations & Grouping?
- Key concepts include: group by, having, count, sum, avg, aggregate, conditional aggregation. These frequently appear in sql & databases interviews at product and infrastructure companies.
- How many questions are in the check?
- Each check has 10 questions — a mix of MCQ and short-answer. You get scored by dimension (e.g., scalability, consistency) so you know exactly where to focus.
- How long does it take to study Aggregations & Grouping?
- Most engineers spend around 2 hours on this module. The check itself takes about 10–15 minutes. You can retake it up to 3 times per day.
- What prerequisite knowledge do I need before Aggregations & Grouping?
- Aggregations & Grouping builds on Joins & Relationships. Complete those first for the best results.
- Is group by, having, count covered?
- Yes. The Aggregations & Grouping module covers group by, having, count among other key concepts. The check includes questions that reflect real sql & databases interview patterns.