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Write a SQL query leveraging window functions and timestamps to identify updates over time

SQLmedium0.3 min readPremium

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Key Concepts Tested

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Expert AnswerPremium

69 wordsInterview-ready

SELECT id, value, LAG(value) OVER (ORDER BY timestamp) AS prev_value, value - LAG(value) OVER (ORDER BY timestamp) AS delta FROM table ORDER BY timestamp. For change detection: SELECT *, LAG(column) OVER (PARTITION BY id ORDER BY updated_at) AS prev, CASE WHEN column != LAG(column) OVER (...) THEN 'changed' END AS change_flag. **Why**: LAG gives previous row; compare to detect changes....

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