Ethan Zhao contributed to the MariaDB/server repository by addressing a critical bug affecting SQL query correctness, specifically in the handling of rownum within HAVING clauses and subqueries. Using C++ and SQL, Ethan updated the accepted_rows logic to ensure accurate row counting in edge cases without GROUP BY, and prevented subqueries from being incorrectly transformed into semi-joins when rownum was present. This work reinforced the reliability of analytics and reporting workloads that depend on precise rownum semantics. Ethan’s approach demonstrated careful debugging and a strong understanding of database development, aligning code changes with repository standards and comprehensive regression coverage.