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Problem solution · SQL

Find Bursty Behavior

Find Bursty Behavior: a SQL solution using relational aggregation. Learn the idea, check the complexity, and read the full code, with credit to walkccc LeetCode Solutions.

Technique
Relational aggregation
Source
walkccc LeetCode Solutions
Length
30 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Relational aggregation

For Find Bursty Behavior, the query transforms and combines relational rows, then filters or aggregates them into the requested result.

  1. Identify the source rows and join keys.
  2. Apply filters before aggregation when possible.
  3. Group, rank, or project the final columns required by the result.

Code notes

  • 30 lines of SQL from the credited upstream file 3089.sql.
  • The implementation keeps its working state in language-native values and containers.
  • No explicit loop blocks detected.

Complexity

Review join cardinality, grouping keys, and available indexes when estimating query cost.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from walkccc LeetCode Solutions by P.-Y. Chen (walkccc) and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeFind Bursty Behavior · SQLSQL
Use this to learn the idea, then write your own version.
WITH  SevenDayPostCounts AS (    SELECT      Post1.user_id,      COUNT(*) AS post_count    FROM Posts AS Post1    INNER JOIN Posts AS Post2      USING (user_id)    WHERE Post2.post_date BETWEEN Post1.post_date AND DATE_ADD(Post1.post_date, INTERVAL 6 DAY)    GROUP BY Post1.user_id, Post1.post_id  ),  AverageWeeklyPosts AS (    SELECT      user_id,      COUNT(*) / 4 AS avg_weekly_posts    FROM Posts    WHERE post_date BETWEEN '2024-02-01' AND '2024-02-28'    GROUP BY 1  )SELECT  SevenDayPostCounts.user_id,  MAX(SevenDayPostCounts.post_count) AS max_7day_posts,  AverageWeeklyPosts.avg_weekly_postsFROM SevenDayPostCountsINNER JOIN AverageWeeklyPosts  USING (user_id)GROUP BY 1HAVING max_7day_posts >= avg_weekly_posts * 2ORDER BY 1;

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