Can You Solve Redfin’s SQL Puzzle?
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🧠 Weekly Challenge
Redfin Wants Your SQL Skills: Update Call Duration
Redfin helps clients to find agents. Each client will have a unique request_id and each request_id has several calls. For each request_id, the first call is an “initial call” and all the following calls are “update calls”. What's the average call duration for all update calls?
This SQL challenge from Redfin asks you to calculate the average duration of all update calls for each client request. You'll sharpen your skills in window functions, filtering ranked data, and aggregate calculations.
Approach Hints
To solve this SQL challenge on your own, consider these technical points:
Use the window function RANK() to rank calls within each request_id group.
Apply PARTITION BY request_id to ensure rankings reset for each client's request.
Order the rankings by created_on to correctly identify the first (initial) call.
Filter your ranked subquery to select only update calls (rk > 1).
Compute the average using the AVG() aggregate function on call_duration.
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