I have a technical interview coming up for a Junior Data Analyst position at a logistics firm. I’ve been practicing on LeetCode, but I’m curious about what US-based companies actually ask in real life. Do they focus more on complex JOINS, or should I be worried about Window Functions and Subqueries? Since I don't have a degree to back me up, I know I need to ace the live coding portion to prove I actually know how to manipulate relational databases.
3 answers
For junior roles in the US, you will almost certainly get a question on JOINs (know the difference between LEFT and INNER) and GROUP BY clauses with aggregation functions like SUM or AVG. However, many mid-sized companies are now including at least one question on Window Functions, specifically RANK() or LEAD/LAG. They want to see if you can compare month-over-month growth or find the top-selling product in each category. My advice: practice writing clean, readable code and always explain your logic out loud. Showing you understand the "Business Logic" is just as important as the syntax.
Are you also preparing for behavioral questions that ask about a time you found an error in your data? Often, the technical test is just a "pass/fail," and the final decision comes down to how you handle "messy" data scenarios.
Don't forget Common Table Expressions (CTEs). They make your code much more readable than nested subqueries, and US senior analysts usually prefer seeing them in a technical screen.
CTEs are a lifesaver for organization. Using "WITH" clauses definitely makes you look like a more seasoned pro during the coding challenge.
That’s a great reminder, Jeffrey. I actually had an interview where the SQL part was easy, but I stumbled when they asked how I would handle null values in a dataset. I’ll make sure to prep my "data cleaning" stories.