DataLemur, SQL interview practice

DataLemur is an interview practice site at datalemur.com, built by Nick Singh, who wrote Ace the Data Science Interview and previously wrote SQL at Facebook. You get company-style questions, an editor to run them, hints, and a worked solution. A lot of the catalogue is free; some solutions and extra questions sit behind a paid tier.

What it is for

Timed, messy questions: window functions, more than one grain, a prompt that looks like a take-home. That is a different muscle from a tutorial lesson.

I use it when I want to see whether I still write a clean window, or when I am helping someone who has an interview date. I do not use it to learn SELECT from zero.

What it is not

It is not a warehouse. The dialect and the grader are for practice, not for a production procedure.

SQLBolt and Select Star SQL teach the language. SQL Case Files makes you investigate. DataLemur asks interview questions. I keep them in that order.