Only Here

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

Domain

SQL

Difficulty

hard

Seniority

L5

Problem

The ML team is isolating features that live only in the 'transactions' source and never surface in 'page_views' or 'ad_impressions', where two entries describe the same feature when they share a name and a data type. Those data-type labels were recorded inconsistently, so spellings like 'INT64' and 'int64' stand for the same type and count as one. A feature is logged many times, so collapse its entries into a single row reporting 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 checks it automatically.