Aggregation
3 Topics
1
COUNT, SUM, AVG, MIN, MAX
Summarize data using the five core aggregate functions.
Aggregate functions are foundational SQL interview topics — interviewers test your understanding of how COUNT handles NULLs, the difference between COUNT(*) and COUNT(column), when to use DISTINCT inside aggregates, and how aggregates interact with GROUP BY.
2
GROUP BY Clause
Partitioning rows into groups for per-group aggregation.
GROUP BY is one of the most frequently tested SQL concepts — interviewers evaluate whether you understand what can appear in SELECT, how multi-column grouping works, and how GROUP BY interacts with WHERE, ORDER BY, and JOINs.
3
HAVING Clause
Filtering aggregated groups based on aggregate conditions.
HAVING is a classic interview topic — interviewers use it to test whether you understand the difference between WHERE and HAVING, when aggregate filters are evaluated, and how to combine HAVING with complex multi-aggregate conditions.