SQL for Data Analysis

Write correct, fast analytical SQL — joins, windows, cohorts, funnels and the traps that silently corrupt numbers

Master analytical PostgreSQL: query evaluation order, join fan-out traps, CTEs, window functions with frames, date bucketing, cohort retention, funnels, sessionisation, NULL pitfalls, CASE pivots, deduplication and the classic SQL interview questions.

Practice questions (6)

• The Revenue Number That Tripled Overnight

  Beginner · Free
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• Users Who Never Purchased Returns Zero Rows

  Beginner
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• The Running Total That Jumps in Steps

  Intermediate
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• Build a Weekly Retention Table

  Intermediate
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• Sessions from an Event Log, Then a Funnel

  Intermediate
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Quizzes (1)