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$ curl repovive.com/roadmaps/data-engineer-interview-prep/sql-mastery-for-data-engineers/running-totals-and-averages

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Running Totals and Averages - SQL Mastery for Data Engineers | Data Engineer Interview Prep | Repovive

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Data Engineer Interview Prep16 sections · 140 units8h total

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Running Totals and Averages

Common interview pattern

Running calculations appear frequently in interviews.

Running total:

SELECT date, amount,
  SUM(amount) OVER (
    ORDER BY date
    ROWS UNBOUNDED PRECEDING
  ) as running_total
FROM transactions

Moving average ( $7$ -day):

SELECT date, amount,
  AVG(amount) OVER (
    ORDER BY date
    ROWS BETWEEN 6 PRECEDING AND CURRENT ROW
  ) as moving_avg
FROM daily_metrics

Know the frame clauses: ROWS vs RANGE, UNBOUNDED vs N PRECEDING.