Back From the Brink

A hard SQL interview practice problem on DataDriven. Write and execute real sql code with instant feedback.

Domain

SQL

Difficulty

hard

Seniority

L5

Problem

Each row in deploy_logs is one deployment: the engineer who ran it (author), a status, and a deploy_at timestamp. The same engineer sometimes shows up under different name casing, and status is logged in mixed casing too, so treat both case-insensitively. Line up each engineer's deployments in time order and count the different engineers who bounced back at least once, meaning a rolled_back deployment whose very next deployment succeeded.

Summary

Roll it back, then nail the next one.

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