Only Here

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

Domain

SQL

Difficulty

hard

Seniority

L5

Problem

The ML team is isolating features that live only in the 'transactions' source and never show up in 'page_views' or 'ad_impressions', where two entries describe the same feature when they share a name and a data type. A feature is logged many times, so collapse its entries into one row and report the feature name, data type, mean recorded value, and mean null percentage, ordered by feature name.

Summary

Exclusive to one source. Missing from the other.

Practice This Problem

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