1.  Can practice coding challenges with [codility](https://app.codility.com/programmers/) since this a platform used for coding challenges. Challenges in different programming languages, but unfortunately not in SQL.
2. A list of technical question [here](https://github.com/alexeygrigorev/data-science-interviews/blob/master/technical.md#sql), which includes SQL, python and algorithms.
3. [Interviewbit](https://www.interviewbit.com/sql-interview-questions/) offers a long list of scenario SQL questions one can study from along with practice with a couple of multiple choice questions.
4. [Pgexcercises](https://pgexercises.com/) is a good platform that provides a dataset and an extensive series of postgreSQL queries to practice with.
5. [This article](https://www.analyticsvidhya.com/blog/2017/05/questions-sql-for-all-aspiring-data-scientists/) provides 42 SQL questions one can study from.
6. Initial questions about SQL at an interview:
  * What functions do you know in SQL?
  * How do you use `SELECT` in a query?
  * How do you use `JOINS` in a query?
  * How would you write in example query with `SELECT` and functions?