Two-Way Street

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

Domain

SQL

Difficulty

medium

Seniority

L4

Problem

In chat_msgs, each reply records the user who wrote it in sender_id and the user being replied to in reply_to, which is empty for messages that are not replies. Count the unique two-person conversations, where a reply from one user to another is the same conversation no matter which of the two sent it.

Summary

A conversation reads the same from either side.

Practice This Problem

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