What Interviewers Are Actually Looking For in a SQL Screener
The SQL screener is probably the most misunderstood interview stage in data hiring. Candidates treat it like is only a SQL test. It's not
The SQL screener is probably the most misunderstood interview stage in data hiring. Candidates treat it like is only a SQL test. It’s not.
It’s a simulation of the first week on the job. Can this person take a vague business question, sit down with a dataset they’ve never seen, and get to an answer on their own?
That’s it. That’s what I’m evaluating.
What the SQL screener actually looks like
The format
The format varies by company, but the core is always the same: you get a dataset, one or many business questions, and somewhere between 30 and 60 minutes to write SQL that answers it.
The tools
Some companies use platforms like HackerRank or CoderPad, where you type into a browser-based editor and run queries against a pre-loaded database. Others do it over a video call with a shared screen — the candidate works in their own SQL environment while the interviewer watches. A few will hand you a schema diagram and sample data and ask you to write queries without executing them, though that’s less common now.
The questions
The business question is usually something like “find the top 10 customers by revenue in the last 90 days” or “calculate the month-over-month retention rate for users who signed up in Q1.” Sometimes there’s expected output to compare against. Sometimes there isn’t, and part of the evaluation is whether you can figure out what the answer should look like.
What the interviewer is watching
On the interviewer side, I’m watching everything. Not just the final query — how you read the problem, how long you spend before typing, whether you explore the schema, how you react when something breaks. The SQL is the artifact. The process is the evaluation.
Writing SQL is part of it, obviously. But it’s the minimum. What I really want to know is: can you operate independently? Can you read a problem, figure out what’s actually being asked, make decisions about how to approach it, and unblock yourself when something goes wrong? Because that’s what the job looks like every day. Nobody is going to sit next to you and tell you your JOIN is wrong or that you misread the requirements.
The candidates who pass aren’t always the ones who write the best SQL. They’re the ones who show me they can think through a problem end to end — from understanding what’s being asked, to writing something that works, to catching their own mistakes.
The ones who struggle usually aren’t struggling with SQL. They’re struggling with everything around it: reading the problem carefully, asking the right questions, talking through their approach, debugging when things break, and noticing edge cases that would bite them in production.
If you’re preparing for a SQL screener, stop thinking of it only as a coding test. Think of it as: “can I convince this person I’d be productive on day one?”
That reframe changes how you prepare.
Know someone interviewing for data roles right now? Send this their way. Understanding what the interviewer is actually looking for changes everything about how you prepare.
If you want to practice this in a live setting with real feedback, I’m working on something. DM me “SQL“ and I’ll keep you posted.
this is great! communication weighs more than correct syntax itself. I felt the most challenge ones are writing in a google-doc style and with no sample data but only table schema provided. I would have to imagine the results in my head. Btw, I am curious what the SQL practice platform you recommend? I have heard the leetcode might be the most ideal. thank you!