Why Are You Failing Your SQL Interviews? (2024)

As data literacy increases in importance, we’re going to see more and more SQL interviews for roles beyond data science. Unfortunately, these interviews can be intimidating, tricky, and tough — especially if you’re just learning SQL for the first time.

From my experience doing hundreds of SQL interviews, this article covers the 5 most common mistakes that I’ve seen. While some may seem obvious, I’ve interviewed enough candidates from a variety of backgrounds where I think that it’s worth discussing each separately. I believe that any candidate who has solid SQL fundamentals and are able to avoid these 5 mistakes can pass any SQL interview.

While there could be different definitions of a “SQL interview”, generally it is a thirty minute to hour long interview where the main focus is to write SQL code to query data from a database. Questions like “What percent of Uber Drivers had an average star rating of 4.70+ in the last month” or “What 10 stores have the most Yelp 5-star ratings in Chicago?” are common.

While I’ve seen many people breeze through these interviews, I’ve also interviewed a lot of candidates who struggle through the interview. While small mistakes seem trivial, they may end up being the deciding factor on whether a candidate moves on.

This is by far the most common mistake that candidates run into. You can think of a SQL interview as an exam, with two big differences.

In an exam you usually will have all the questions listed up front. This means that you can spend a few minutes at the beginning of the exam to get a sense of how you might allocate your time, which may influence how you answer certain questions or skip questions to get the best score possible.

In a SQL interview, the differences are:

1. Only the interviewer will know the questions, and they will reveal them one-by-one
2. There is no skipping around

This makes time especially important — because you don’t really have an idea how many questions there…