SQL Interview

SQL interview questions on joins, keys, aggregation, subqueries, indexes, transactions and normalisation.

4 notes

Notes

The questions asked in almost every SQL interview, with short answers you can actually say out loud and the follow up the interviewer will ask next.

GROUP BY rules, HAVING versus WHERE, the NULL behaviour of aggregates, and the subquery questions that separate confident answers from vague ones.

The performance and concurrency half of a SQL interview: how indexes work, what they cost, ACID, isolation levels and deadlocks.

Design and correctness questions: the normal forms, why NULL breaks intuition, and how to answer "this query is slow, what do you do?"