Rooms in Common

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

Domain

SQL

Difficulty

hard

Seniority

L5

Problem

We map user networks through our chat channels: two people count as connected the moment they've both posted in the same channel, no matter how many channels they end up sharing. For each sender, find how many other people they're connected to, most-connected first.

Summary

Two people, one channel, a connection you never counted.

Practice This Problem

Solve this SQL problem with real code execution. DataDriven runs your SQL queries against a real database and checks it automatically.