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Top K Users From Chat Logs (SQL)

MediumSQL · PostgreSQL00:00
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Your question is Top K Users From Chat Logs (SQL). Start with the requirements and the one table on the right.

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Problem

Given chat logs, find the top k users with the most frequent chat activity.

Asked in the Virtual Onsite stage. A variant of Top K Frequent Elements (LeetCode 347). Discussed merge sort, max heap, and quick select approaches, including pseudocode, time complexity, and space complexity analysis.

Task

Write a SQL query to return the top k users by message count from a chat log table.

Requirements

  1. Count chat messages per user.
  2. Rank users by message count descending, then by user_id ascending for ties.
  3. Return only the top k users.

Output

Schema

chat_logs
ColumnTypeDescription
log_idPKBIGINTUnique chat log row identifier
user_idBIGINTUser who sent the chat message
message_idBIGINTUnique message identifier
sent_atTIMESTAMPTimestamp when the message was sent
Tableschat_logs
Your solutionPostgreSQL
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