HackerRank data engineering interview questions screen on a tight, predictable skill matrix: SQL JOINs with foreign-key filters, multi-table aggregation without fan-out, GROUP BY / HAVING on related-row predicates, window functions for streaks and per-day winners, CASE on hierarchies for tree-style classification, scalar subqueries with strict output formatting, and PySpark dataframe transforms the platform now grades alongside SQL. The grader is exact-match on stdout — clever logic with the wrong trailing zero fails the test case. This guide walks through the seven canonical clusters HackerRank actually tests for data engineers, drawing on its own 7 Advanced SQL Interview Questions set plus first-hand candidate reports for the company's online assessment.…