SQL Quest

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SQL Interview and Career Preparation

A practice-heavy preparation track for SQL interviews and take-home tests. You learn a repeatable method for live questions (clarify, explore, build in steps, think aloud, test edge cases), then work through the classic patterns interviewers use: second highest values, duplicates, top-N per group, running totals, month-over-month growth, gaps and islands, medians, pivots and recursive hierarchies. Every lesson switches dataset, so you practise reading unfamiliar schemas quickly. Debugging and query-review lessons train you to spot the mistakes interviewers see most often, a business-case lesson and an analytics case study connect SQL to decisions, and a mini take-home project rehearses the full workflow from brief to final result. Role notes explain what analyst, BI, finance and data engineering interviews emphasise.

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Lessons

  1. How SQL interviews workA repeatable method for live SQL questions: clarify, explore, build in steps, think aloud and test the edge cases before you say 'done'.22 min · 4 exercisesFree
  2. Classic beginner interview questionsThe screening questions almost every SQL interview starts with: Nth highest value, duplicates, counts with zeros, 'did X but not Y', self-joins and distinct counts.30 min · 6 exercises Members
  3. Analyst-level interview questionsThe second round: latest record per entity, top-N per group, running totals, month-over-month growth, medians, pivots and pairs.40 min · 7 exercises Members
  4. Advanced interview challengesThe hard round: gaps and islands, consecutive-day streaks, recursive hierarchies, Pareto shares, repeat-purchase cohorts and rolling averages over a date spine.45 min · 6 exercises Members
  5. Debugging queries under pressureA systematic way to fix queries that fail loudly (errors) and, more importantly, queries that run but return the wrong answer.30 min · 6 exercises Members
  6. Matching a specification and explaining itTurn a precise written specification into a query that matches it clause by clause, then narrate that query clearly in the order the database runs it.30 min · 5 exercises Members
  7. Business case questionsTurn open business questions from a bank and a SaaS company into precise metric definitions, defensible queries and a one-sentence answer.40 min · 6 exercises Members
  8. Analytics case study: a board pack from a star schemaWork through a full analytics case on the Wadi Market mart: fiscal-year results, like-for-like growth, the funnel, seasonality, marketing return and new versus returning customers.45 min · 6 exercises Members
  9. The mistakes interviewers see mostSix mistakes that cost candidates offers, each as a query to fix: COUNT(*) after LEFT JOIN, WHERE instead of HAVING, BETWEEN on timestamps, DISTINCT hiding fan-out, averages at the wrong grain and LIMIT for top-N per group.30 min · 6 exercises Members
  10. Mini take-home: account health reportA complete take-home assignment on Mizan Cloud: audit the data, define the paying base, measure usage and support exposure, flag at-risk accounts and deliver a final health summary.55 min · 6 exercises Members