Insights from Student Solutions to SQL Homework Problems

We analyze the submissions of 286 students as they solved Structured Query Language (SQL) homework assignments for an upper-level databases course. Databases and the ability to query them are becoming increasingly essential for not only computer scientists but also business professionals, scientists, and anyone who needs to make data-driven decisions. Despite the increasing importance of SQL and databases, little research has documented student difficulties in learning SQL. We replicate and extend prior studies of students' difficulties with learning SQL. Students worked on and submitted their homework through an online learning management system with support for autograding of code. Students received immediate feedback on the correctness of their solutions and had approximately a week to finish writing eight to ten queries. We categorized student submissions by the type of error, or lack thereof, that students made, and whether the student was eventually able to construct a correct query. Like prior work, we find that the majority of student mistakes are syntax errors. In contrast with the conclusions of prior work, we find that some students are never able to resolve these syntax errors to create valid queries. Additionally, we find that students struggle the most when they need to write SQL queries related to GROUP BY and correlated subqueries. We suggest implications for instruction and future research.