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Find each user's longest streak of consecutive active days in SQL (gaps and islands).

Consecutive-run problems (active streaks, uptime windows, price-stable periods) all reduce to one trick. Once you see the row-number difference, they collapse to a window function and a group-by.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.

Consecutive-run problems (active streaks, uptime windows, price-stable periods) all reduce to one trick. Once you see the row-number difference, they collapse to a window function and a group-by.

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Next in this trackDo vector similarity search inside SQL (pgvector / warehouse). When is this the right call?Next in this trackPull a random sample, and a stratified sample, for an ML training set in SQL.Next in this trackGenerate ML labels in SQL: did each user churn (no activity in the next 30 days)?

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