The Vanishing Rows

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

Domain

SQL

Difficulty

easy

Seniority

L3

Problem

A downstream dashboard is reporting fewer content views than expected. The content_views table has 100 records, but some views were logged without a user association. Write a query that pairs content_views to users on user_id and returns each view's ID, user ID, and username. Then reason about why the result has fewer than 100 rows.

Summary

Some records disappear when the tables meet. Figure out why.

Practice This Problem

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